This 600/1,000 grit is my second Unimi knife sharpener, the first is 2,000/6,000 grit and I love them both. Both stones together produce very sharp and well polished knives that reduce the cutting effort and save time in the kitchen. I particularly appreciate that the manufacture printed the grit number on the side of each stone - that helps use the different grits in the proper sequence from the coarser to the finer. The stone comes with a non-slip silicone/rubber base which is very handy.
Today, however, there is a whole new generation of mechanical sharpeners that are far more forgiving for those who may not use perfect technique. At the same time many more people have become accustomed to sharpening their knives this way and the average novice of 10 years ago is now the seasoned pro. It is still possible to damage knives with an electric sharpener, but you would have to either be trying to damage the knife or have some type of accident in order to do so.
1. Diamond Stones. I’ve used two, many years ago, to sharpen steel knives & found that the diamond coating wore away. They did work well at first, but then I was sharpening on the backing material. This puzzled me, because diamond is harder than steel, but have only recently read that the diamond particles are torn off the backing material because they stick to the softer steel. Diamond stones are recommended for sharpening ceramic knives only. This info about diamond stones & steel knives I got from an Edge-Pro article.
Why, then, do so many of us shy away from the task? To put it bluntly, it's because it's a rather daunting process for the beginner. Your image of knife sharpening may consist of a hyper-masculine chef slashing away violently at a steel rod (we're looking at you, Gordon). Conversely, you might have seen cooks meticulously and methodically stroking their blade up and down a Japanese waterstone with more intricate attention to detail than a Flemish landscape. 
I give Sharp Pebble a top rating for two reasons. First, the company emailed a user guide for me to review and learn how to best use its product while it was being shipped to me. Wonderfully proactive. Second, the sharpening stone did a terrific job restoring the edge on my kitchen knives that had been woefully neglected. Ever rent a house and every knife in the kitchen has the edge of a butter knife? I was almost there. Now, the knives are cutting beautifully. I have only one suggestion for Sharp Pebble. While the stone includes a useful angle guide that can be attached to a blade and the guide gives clear steps on prepping the stone and how to hold the blade when sharpening, it does not illustrate the manner in which the blade needs to be moved across the stone. I had to go to Youtube to get some tips on the exact method. I have historically been very bad at putting an edge on a blade due to ignorance primarily. But with the help of the video and a good stone, I did an effective job. The base does a great job of holding the stone in place and is attractive in the kitchen.
Actually, the company contacted me to make sure I received the stones and that I was happy with them. Excellent service. The stones are great! I'm pretty much a novice so the clear instructions that came with the stones and the eBook instructions were wonderful. The eBook had quality pictures demonstrating the use of the stones and the written instructions were clear and to the point. Within minutes of opening the box I had the stones figured out and sharpening my AF survival knife, my pocket knife and a couple of my wife's kitchen knives...which included a very expensive chef's knife. Very satisfied with this product and highly recommend it.
I purchased this set together with the 400/1000 grit stone assuming that some of my knives were quite dull and would need work on a coarse grit stone. Premium Whetstone Sharpening Stone 2 Side Grit 400/1000 | Knife Sharpener Waterstone with NonSlip Rubber Base & Flattening Stone. This is my first wetstone. First off I tried to sharpen my Chicago Cutlery boning knife. This knife is nearly thirty years old, has been abused in may ways and was quite dull. It was very difficult for me to get a burr on this blade, which I attribute to poor technique. Next I moved on to my Henckels Professional S paring and chef's knives. The paring knife was moderately sharp and was modestly improved after working over all three grits of stone. It would cut paper but again it was difficult to develop a burr with this blade. Undaunted I switched to the chef's knife. This knife is twenty years old and has never been professionally re-sharpened. I have sharpened it twice with a Lanksey sharpening system which marred the finish but did put a good edge on the blade. Lansky Standard Coarse Sharpening System with Fine Hones. The chef's knife was moderately dull and had several pits visible on the cutting surface. I modified my technique for passing the knife over the stone and worked the chef's knife over the 400 grit stone aggressively and eventually I was able to get a burr to form from the tip of the knife all the way to the handle. From there it was a simple process of reforming the burr on the 1000 grit stone and then finishing on the 6000. After sharpening, the chef's knife easily and cleanly slices a tomato with very light pressure and is in my opinion very sharp. Not sushi knife sharp but more than enough for the chopping and slicing I expect of it. I'm looking forward to going back and working both the boning knife and the paring knife over again. Don't expect a good result from this product the first time you use it. Watch videos on using a wetstone, expect to spend at least twenty minutes per knife at first, and practice forming a burr. If you can form a burr, you will be able to successfully sharpen your knife.