Whether Japanese or German knives this 10,000 grit glass water sharpening stone is an excellent way to maintain your knives' razor-sharp edge, to a scalpel-like sharpness. As with most stone sharpeners, this does take some practice but can easily become one of your favorite maintenance activities. This is the next level of stone sharpening, steppping up gradually to start grinding coarse from a lower gritstone from 400, and stepping to 1,000 gritstone, is typically used to repair knives up to 3,000 grit is used to sharpen dull knives. And either finish to that or with the higher grit up to 5,000 grit are finishing stones and are used to refine your knife edge but if you want to go higher up to 10,000 then go for it. Depending on the knife hardness and edge, it is a personal preference and needs to use a higher gritstone. The only bit of advice you should follow is this: "If you are using your knife to cut meat, then you can happily stop at 4000 or 6000 grit. If you are only using it for vegetables or fruit go all the way to the 8000". It is advisable to start from a lower grit to sharpen your knife and finish with the higher grit. I suggest practicing on an inexpensive knife first when you are just getting the feel for stone sharpening. But it is totally worth the time and money for that perfectly clean cut. It just elevates the entire cooking experience when you have a really sharp knife for every cut. Practice makes it perfect!