This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. Every review you see on this blog is bought with my own money. I have no affiliation to any manufacturer. As this is a review of my own product, you could consider this an advertisement. I have applied the same scientific principles and morale vigor as I do to every review – nevertheless, I feel like I should mention: this is WERBUNG.

Review

I know – I know. We’ve had this before:

A brief study on sharpening stones – Part 30 – Dr. Marv’s Scientific Sharpening Stone, 2.5 µm

The thing is – I am a big fan of Kaizen (改善). You see, one reason why I started making abrasives was my frustration with the quality of abrasives on the market. And that desire to improve, to innovate is a constant in my actions. When I launched my sharpening stones a year ago, I was quite happy with the performance – it felt, and still feels like a very, very high performance abrasive. But time hasn’t stood still – I have constantly improved. Compared to a year ago, the stones are cleaner. They are nicer made. Distribution of particles has been fine tuned, improved and the concentration varied until it hit a sweet spot.

Moreover, in the reviews, I’ve acquired and started to incorporate better metrology – and last but not least, I still owe the reviews for the 1 and 0.5 µm stones.

Therefore, I felt like it was time to update the review.

Let’s start with the outer part: 4 mm blank, fully black anodised. Cleaner interface between stone and resin.

Moreover, after having a small batch (produced at the end of 2025) that had a tendency to come apart when stored improperly, I have improved on the bonding technique. The aluminium blanks now feature mechanical interlocking, laser structuring and are plasma cleaned. It has increased bond strength between the abrasive and the blank so much that I actually can’t take them apart, no matter what I tried. I am very convinced that any future purchases will be very strongly bonded and not come apart.

There’s a new case design, that’s a bit smaller and sleeker. The engraving now features a very proud “Made in Germany” on it, and has also improved in quality and resolution by switching from a blue diode to a MOPA laser.

Let’s take a look under the optical microscope!

Optical micrographs of the stone. Instrument: Marvscope

The stone still features what I believe is important – diamond, the binder and nothing else. This is already very apparent at the high resolution optical microscopy shot above.

Let’s take a closer look in the SEM:

SEM micrographs of the 2.5 micrometre stone. Instrument: Zeiss GeminiSEM 560.

The picture above is taken from the dressed, factory new surface of the stone. We can see a very fine distribution of particles, with no apparent clumping. The funny thing about such small diamond particles is – because the molecular weight between binder and diamond is so identical, contrast is very low, and we can’t really see them visually if they are hidden below the binder. If you compare this with the optical image above, it seems like the concentration is much lower. Fortunately, one can “make” the SEM look “deeper”, by increasing the accelerating voltage. Then, the electrons start to tunnel, and go further into the material, increasing the interaction depth.

This is exactly what I did for the EDS measurement – we now have interaction not just on the very surface of the specimen, but also much deeper – a couple of microns deep! This immediately shows the high concentration of the stone:

EDS analysis of the stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

Something I want to highlight here – the distribution is frankly outstanding for such a small stone. First, there is no parasitic particle, no foreign abrasive or anything but the carbon that forms the diamond visible. Moreover, if you look at the spacing and clumping of the 2.5 micron particles – I am personally speechless. There is no agglomerate whatsoever and a very fine distribution.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. I am using a standardised testing procedure, read about it here. Nevertheless, it’s 65 HRC M398, and sharpened to 17 DPS with resin bond diamond stones down to 5 µm. Afterwards, the tested stone is used, first in a back and forth movement until the surface becomes homogenous, and then alternating, edge trailing strokes (5-5-3-2) on each side, for a total of 20 strokes towards the apex per side. No pressure is applied but the weight of the apparatus. ´

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

SEM micrographs of the M398 edge finished with the stone. Instrument: Zeiss GeminiSEM 560

We can see a very smooth surface. There are some nanometric scratches remaining, only visible at the higher magnifications. The whole bevel has a polished appearance to it – the carbides of M398 are wonderfully visible. A fine, sub micrometre apex is also visible, with no apparent burr at the magnifications shown.

Optical micrograph of the M398 bevel. Please note the increased magnification compared to other reviews – this is at the limit of optical microscopy. Instrument: Marvscope

The optical high resolution shot shows a similar image – very visible carbides, and sub micron scratches. This is a wonderful, very regular result for a mirror-like apex. The blade itself is blazingly sharp – just like it should be!

A sidenote: I have been constructing my own microscope for quite some time, to have better optical images. The above image is as far as I remember the first high resolution shot on the blog – taken with a fantastic NA 0.8 lens. I’ll do a post on the build and microscope in a few months, but can proudly state: I have achieved diffraction limited resolution with that build.

Let’s take a look at the WLI height map:

3D surface height map of the M398 Bevel. Instrument: Zygo NewView 9000, Objective Lens: 50X. Metrological filter chain: LS-Plane to orient data, cutoff 0.25/99.75 percent to remove outliers.

The white light interferometric measurement shows a near constant shape over the observed region – this is a very flat (sub 0.1 µm) bevel! Moreover, very little stray scratches are detectable,

With the surface roughness parameters as follows:

Sa	0.0042	µm
Sq	0.0053	µm
Ssk	0.2987	–
Sku	2.913	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.025 mm (gaussian). No F operation besides LSQ leveling.

A single digit nanometric surface roughness is approaching optical specifications – and is a stunning statement to the cleanliness of this stone.

The stone itself still is “quick”, for it’s micron rating. There’s a bit more feedback than on previous generations.

Let me be very clear here though: If you already are a customer and have a fine set, there is very little sense in upgrading. Don’t have regrets because you bought an earlier set – they are fantastic, high performing and stelar abrasives. The performance gain on this on, just like every time you approach peak performance, is of course of the diminishing kind. It’s not 100% better than the previous ones, but a constant improvement over time – in the spirit of Kaizen!

If you don’t have one already – this stone probably is the reason why I make abrasives. It is spectacular, so clean – increasing sharpness, gloss and finish of a bevel by a wide margin. I love it and it gets used on every knife I sharpen for myself.

This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. The stones in this review were a gift from the manufacturer.

Review

Today’s sharpening stone is something very special. I’m frankly quite giddy as I am writing these lines – gentle readers, I am ecstatic to present you the review on the brandnew “Grain&Bond” – Sol Gel (SG) Sharpening stones – from Likhovtsov Abrasives Lab.

These sharpening stones were launched in the past 24 hours. They are the product of Alexander Likhovtsov, someone I consider a master in abrasives from Russia. The stones reviewed are two different grit sizes, F120 (120 µm) and F220 (63 µm).

Let’s dig into it:

The bright blue “F120” and “F220” SG stone. Do note: The stones being sold have a different laser engraving on the anodised aluminium blank.

The “SG” stands for sol-gel, the production process of the Al2O3 (Corund) abrasive these are based on. To expand, why this is exciting, you have to understand how aluminium oxide as an abrasive is made:

There are basically two methods in producing the popular abrasive. Large scale, one can melt Al2O3 into a large block, cool it down and then crush it into small pieces. These are then sorted by size, which makes for a very economic, hard powder. The individual grains themselves consist of only a few crystals, often micrometre sized.

The second industrial method is to mix precursors together, dry them until they form a gel, and then sinter the mixture before crushing and sorting for size. Here, each individual grain is polycrystalline, consisting out of a large number of often nanometre sized crystallites.

In their behaviour, they differ wildly. The molten Al2O3 dulls, and at some point fractures into large segments. The sol-gel Al2O3 meanwhile constantly exhibits micro fractures, that renew the cutting edge. This gives less of a glassy, dull feel during sharpening, but also a more homogeneous result. The downside to SG-Al2O3 is of course the cost – it costs multiple times more than regular melt-produced Al2O3.

You might ask: how does this translates to visible grain morphology? Don’t worry, I got you covered. Compare the SG grain with a similar sized molten Al2O3 grain, in the same binder:

Comparison in grain morphology between F220 sized grains – left/first picture is the SG-Al2O3, second/right picture is the molten AL2O3.

You can see that the SG-Al2O3 has a much smoother, flatter, and less ragged appearance. The molten Al2O3 initially shows a lot of ragged cutting edges from the crushing of the grain, but is also much more blocky – this is an increase in engagement volume, which makes cutting of hard steels more difficult, and typically quicker leads to a dull, burnishing feeling.

Let’s take a look under the optical microscope!

Optical micrographs of the Grain & Bond SG F120 (first/left picture) and SG F220 (second/right picture) stone. Instrument: Marvscope

The bright blue colour comes through very nicely in the optical microscope images. On the F120 size, we can make out the individual grains very easily. The are elongated, smooth and flat ones. The finer F220 stone meanwhile shows a few more white grains, as well as smaller, more blocky and square abrasive grains.

Let’s take a closer look in the SEM, first for the SG F120:

SEM micrographs of the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560.

The stones shows a large number of grains. They are a mix of flat, elongated grains and some blocky ones with multiple, ragged cutting edges visible. The overall concentration is quite high. Between the grains, we can see a grumbly, very small and dense binder. Some controlled and evenly distributed porosity is visible in the stone, which is a good sign on such a large grit – this gives some space for lubrication and swarf!

Let’s look at the chemical composition! For this we are going to use an advanced SEM technique called EDS. If you want to know more about this, I’ve written extensively about SEM microanalysis here on this blog.

EDS analysis of the Grain & Bond SG F120 stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

The EDS analysis shows a large concentration of AO as abrasive in this stone, with some minor, very small SiC distributed on the surface – I would guess, probably from the manufacturing process. The binder mostly shows carbon – which to me makes this a resin stone? It has a surprising hardness, more on this later.

Next, let us take a closer look at the F220 stone:

SEM micrographs of the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560.

The finer stone shows a high conecntration of grains. They are a bit flatter, and oriented in a random way across the surface. Size is spot on, and it has a very homogeneous distribution.

Let’s take a quick look at the EDS:

EDS analysis of the Grain & Bond SG F220 stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

A bit more trace particles – we can find some magnesium, some sodium and some more silicon. Not quite as pure as the F120 stone, but at the same time: they are in a size where the AO abrasive still dominates the result.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. I am using a standardised testing procedure, read about it here. Nevertheless, it’s 65 HRC M398, and sharpened to 17 DPS with resin bond diamond stones down to 10 µm. Afterwards, the tested stone is used, first in a back and forth movement until the surface becomes homogenous, and then alternating, edge trailing strokes (5-5-3-2) on each side, for a total of 20 strokes towards the apex per side. No pressure is applied but the weight of the apparatus. Moreover, the same approach is repeated with a blade in NitroV at 59-60 HRC.

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

First, let’s take a look at the F120 (120 µm) SG stone:

Let’s start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560

Most AO and natural stones struggle a lot with the M398 I use for my reviews. While sharpening the blade for the analytics, I was quite surprised by the amount of black swarf that was created – but also by the delicate, fine apex. Typically, on non-superabrasive stones, these blades maybe get burnished, but the apex is dulled and rounded over. The SG can’t compete with diamond in this steel – but it leaves all other AO stones I’ve had on this blog far, far behind. I’d say the result is even better than comparable sized chinese OEM diamond resin stones, which is…wild.

THe morphology shows large, burnished sections, but also some clear cutting action near the apex. A couple deeper scratches and a slight waviness, giving a toothy edge can be made out and are of course also reflected in the optical micrograph:

Optical micrograph of the M398 bevel finished with the Grain & Bond SG F120 stone. Instrument: Marvscope

Which is further visible in the white light interferometer measurements of the bevel: a smoothed over surface, with a couple of deeper scratches.

3D surface height map of the M398 Bevel finished with the Grain & Bond SG F120 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

The surface roughness is exceptional for a 120 µm sized stone:

Sa	0.1752	µm
Sq	0.2636	µm
Ssk	-1.605	–
Sku	7.810	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edgefinished with the Grain & Bond SG F120 stone. Instrument: Zeiss GeminiSEM 560

The softer steel is, quite expected, a much better target for the SG stone. We get a very fine apex for this grit size, with a regular appearance and morphology.

Optical micrograph of the NitroV bevel finished with the Grain & Bond SG F120 stone.. Instrument: Marvscope

The optical micrograph shows a super smooth, regular bevel with some toothiness to the cutting edge. It is very pleasing, a matte, regular and homogeneous result!

3D surface height map of the NitroV Bevel finished with the Grain & Bond SG F120 stone.. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With the surface roughness parameters being a bit lower compared to the M398 steel:

Sa	0.1205	µm
Sq	0.1649	µm
Ssk	-1.209	–
Sku	5.458	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Next, we’re going to look at the results of the F220 (63 µm) SG stone:

Let’s start again with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560

The stone improved the surface finish noticeably. The bevel still has some deeper scratches, but overall it is very smooth already.

Optical micrograph of the M398 bevel finished with the Grain & Bond SG F220 stone. Instrument: Marvscope

The optical micrograph shows this in the form of very little contrast – besides the deeper scratches.

3D surface height map of the M398 Bevel finished with the Grain & Bond SG F220 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

Which also is reflected in improved surface parameters:

Sa	0.1498	µm
Sq	0.2226	µm
Ssk	-1.34	–
Sku	7.385	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edge finished with the Grain & Bond SG F220 stone. Instrument: Zeiss GeminiSEM 560

The difference is not quite as stark as it is with the M398 steel, but some refinement can be made out. Moreover, a higher amount of cutting traces instead of burnishing can identified. The apex is further refined – this was already quite the sharp knife!

Optical micrograph of the NitroV bevel finished with the Grain & Bond SG F220 stone. Instrument: Marvscope

The optical appearance of the bevel is a lovely, matte and diffuse, very regular scratch pattern – also exceptionally regular under the WLI:

3D surface height map of the NitroV Bevel finished with the Grain & Bond SG F220 stone. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With quite low surface roughness parameters – keep in mind this is a 63 µm sized stone!

Sa	0.1170	µm
Sq	0.1574	µm
Ssk	-1.113	–
Sku	5.905	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.08 mm (gaussian). No F operation besides LSQ leveling.

The stone itself has a high & wonderful feedback. I’m very much reminded of a Shapton Glass, which (up until this stone!) has been a favourite of mine. The stone pics up speed after a couple of strokes, with some slush being created and accelerating the sharpening action. From time to time, a larger grain comes loose – this can be felt and probably explains the deeper scratches. I found that during the couple of hours I spend with this stone, that the speed stayed identical. The typical glazing over that AO stones experience did not happen on this.

I would classify the binder as resin, based on the chemical composition visible in the EDS, even though it is unbelievably hard. I think this is probably the hardest resin stone I ever had on the blog – and this just screams at the manufacturer that there should be a benchstone coming soon, for the freehanders.

The results speak for themselves – a surface finish, factors better than I would imagine an Al2O3 stone could produce. Still working in what is widely considered a difficult super steel. Sharp edges. Wonderful feedback. Good lifetime. Available in 1×6″ format. Affordable price.This stone, to me personally is the “Shapton killer”.

There is very little that could be improved – and so I can only advise you to buy these, with no idea how you would get about doing this outside Russia. Let’s hope they arrive on our markets soon!

I can only end this review by taking my hat off to Alexander Likhovtsov – Моё почтение! Шедевр!

What a wonderful stone. I love it.

This is part of a series of blog posts – looking into the appearance and composition of commercially available sharpening stones. If you are interested in the previous episodes, check out the archive for them.

If you have some suggestion on what I should look at next, or want to share your super secret DIY stones, I could be persuaded to open the bag of analytical devices… hit me up on Instagram under @marvgro for that.

Disclaimer: I’m not for sale. Every review you see on this blog is bought with my own money. I have no affiliation to any manufacturer.

Review

Today’s sharpening stone is the KDTU Silver CBN. According to the shop where I bought it, it features an “advanced hybrid bond enriched with tin and silver-based components, this stone features a distinctive silver-colored abrasive surface — the defining characteristic of the KDTU Silver Stones Series“

Alright. Sounds good. One thing that immediately stands out to me is the very dark colour of the stone. In a previous review, I quoted the manufacturer who said that discolouration is just something inherent to the stones, but the review proofed that it was a sign of bad mixing. I have high hopes that this stone is now better mixed, and not just coloured black to hide mediocre manufacturing.

Let’s take a look under the optical microscope!

Optical micrographs of the stone. Instrument: Marvscope

The stone shows a dark, grey/silver bond. We can immediately make out black CBN grains, which tend to cluster together. Moreover, there’s some streaks of a bronze coloured material visible as well. Honestly: looks pretty cool!

Let’s take a closer look in the SEM:

SEM micrographs of the stone. Instrument: Zeiss GeminiSEM 560.

The SEM pictures show a fine, very dense bond. The abrasive particles are held tightly inside this bond. They are of a very square and blocky type.

The bond is surprisingly dense for a metal bond – most bronze bonds are a bit looser.

Let’s look at the chemical composition! For this we are going to use an advanced SEM technique called EDS. If you want to know more about this, I’ve written extensively about SEM microanalysis here on this blog.

EDS analysis of the stone. Instrument: Oxford Ultim Max  ∞ 40mm² EDS sensor. Note that our EDS sensor doesn’t show elements lighter than boron.

In the EDS analysis, the dense bond is explained – it consists mainly out of aluminium, with some copper, tin, and zinc. The before-mentioned silver that gives this stone it’s name can also be found – in a sub 1% concentration. Silver often is used as either a flux or wetting agent to enhance grain retention. Moreover, we can find some silicon (Carbide?) particles, which are smaller than the CBN. Zooming out, one can see a decent amount of CBN, with an overall mediocre distribution. There’s some clustering, but at this stones grit this will not be a major issue.

In order to evaluate the sharpening performance and material removal mode of this stone, a blade was sharpened with it. I am using a standardised testing procedure, read about it here. Nevertheless, it’s 65 HRC M398, and sharpened to 17 DPS with resin bond diamond stones down to 10 µm. Afterwards, the tested stone is used, first in a back and forth movement until the surface becomes homogenous, and then alternating, edge trailing strokes (5-5-3-2) on each side, for a total of 20 strokes towards the apex per side. No pressure is applied but the weight of the apparatus. Moreover, the same approach is repeated with a blade in NitroV at 59-60 HRC.

The edge is then analysed in the electron microscope for breakouts and morphological appearance.

Let’s start with the harder steel – the M398 blade:

SEM micrographs of the M398 edge finished with the stone. Instrument: Zeiss GeminiSEM 560

The stone left a smooth bevel finish. We can see major signs of ploughing and burnishing – every track of the abrasive grain shows microburr and prow formation at the side. This is a clear sign of plastic deformation instead of clean cutting action. Zooming in to higher magnifications, we can see that the stone created enough pressure that pieces of the steel broke away or fractured near the apex. Nevertheless, the finish is very homogeneous and quite smooth for such a coarse stone.

This is confirmed in the optical micrograph, showing a very matte, silvery and homogeneous finish (do ignore the water drop stains on it – mea culpa maxima!)

Optical micrograph of the M398 bevel. Instrument: Marvscope

Which is further visible in the white light interferometer measurements of the bevel: a diffuse, marred surface:

3D surface height map of the M398 Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With the surface roughness parameters as follows:

Sa	0.3957	µm
Sq	0.5222	µm
Ssk	-0.608	–
Sku	4.854	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

Overall, this is a decent result in terms of surface finish and bevel appearance, but has not really refined the apex massively.

Let’s take a look at the NitroV edge:

SEM micrographs of the NitroV edge. Instrument: Zeiss GeminiSEM 560

The softer steel shows less cracking and damage near the apex, but we can also make out large, plastic deformed regions – some part of it has just bend over. Moreover, the surface morphology is once again showing the typical plastic deformation associated with burnishing.

Optical micrograph of the NitroV bevel. Instrument: Marvscope

The edge of the blade is quite ragged, even for this grit of finishing.

In the WLI measurement some deeper scratches can be made out:

3D surface height map of the NitroV Bevel. Instrument: Zygo NewView 9000, Objective Lens: 20X. Metrological filter chain: LS-Plane to orient data, cutoff 0.1/99.9 percent to remove outliers.

With a slightly higher surface roughness on this bevel:

Sa	0.4340	µm
Sq	0.5652	µm
Ssk	-0.2213	–
Sku	3.939	–

ISO 25178 surface roughness parameters. S-Filter: 2.5 µm (gaussian), L Filter: 0.25 mm (gaussian). No F operation besides LSQ leveling.

The stone itself is pleasant to use. It has a smooth, high feedback feel to it, and is very aggressive in the beginning. After some sharpening action, it loads and becomes a bit slower, but during my test not massively so. It cleans up with a bit of vigorous rubbing.

If I compare the results with the previous coarse CBN stone review from KDTU, I’d say it’s a small improvement, only detectable under advanced microscopes. Mixing still seems to be an area where KDTU struggles, like most abrasive manufacturers. To me, it feels like the harder bond is much tougher on the apex, but the overall feel in sharpening on this one has improved, as did the surface finish.

This brings me to my biggest issue with this stone & manufacturer:

The Ukranian manufacturers (PDT and KDTU) seem to be huge fans of CBN, which is only understandable seeing that during the soviet era, they were a major producer of CBN and still publish a lot of research on it via the V. Bakul Institute for Superhard Materials, a Ukrainian state founded research center for superabrasives. This is reflected in their marketing campaigns pushing these stones. Moreover, their product strategy seems to be the constant release of slightly improved abrasives, since I’ve had this stone 2 more lines came out. This is fine, but for me as a paying customer, it feels like I constantly need to open my wallet to get the latest and newest -and they all fall short of the competition, with no huge improvements.

There is a plethora of stones that outperform this one – both with aluminium oxide or diamond as an abrasive. While this stone is pleasant to use, I’d say there are better choices available.