The Naniwa Super Stones are made with a resin bond, which allows for a higher level of abrasive particles compared with less expensive methods of stone bonding. The higher abrasive levels contribute to the speed of sharpening. This 400 grit is excellent for establishing a new bevel angle or removing chips from the blade. These are splash-and-go stones, so no need for soaking prior to use. They measure 210mm x 70mm x 20mm. We are happy to be the only US distributor of Naniwa Super Stones that come in the larger 20mm thickness without bases.