I got one of these yesterday for 90 baht, supposedly Japan. Only difference is mine is 6000 / 1000 but the white side is the fine (6000) side. As good as any stone I ever used and sharpened to a razor edge (and I mean shave hair off your arm easily). Only used water. Not sure how long it will last but first impressions unbelievable.
I also have one of those Global ceramic water wheel sharpeners which are expensive but do a superb job. Edge never lasts longer than a week but given the treatment my wife gives our kitchen knives surprised they keep an edge that longi
By the way, anyone wanting a very cheap but excellent set of knives, equivalent to Victorinox commercial knives, same steel mix apparently....Cutlery pro.... very hard to beat. I had a set of Zwillings (too heavy for me) I sold immediately after I tried these. 5 years on and still awesome. If you Google CUTLERY PRO you will find a few suppliers on Lazada, Shopee etc. Havent checked the prices lately but 8 / 10 inch chefs knife or butchers knife under 1000 baht. 5 years on still easy to sharpen and hold a keen edge, handle / joints as good as new and I use them semi commercially every day