Coarse Atoma 140 diamond plate with metal backing. Comes with stone holder.

This stone was manufactured as a coarse sharpening stone, but we much prefer it as a flattening stone for stones at 400 grit and up (very coarse stones can prematurely wear away the plating holding the diamonds).

It especially is great for flattening hard ceramic stones. This is our go-to for flattening here in our shop, as we are using a number of different stones all day. It is great for flattening the bottoms of natural stones however we typically recommend the 400 Atoma for flattening natural stones. Fine stones (3000 grit plus) should be smoothed over with a nagura after using this stone.