This is a 4" round combination Crystolon, or silicon carbide, stone with both coarse and fine sides. The coarse side is very aggressive and is used for bringing dull edges back to sharpness. The fine side is used to restore edges that are slightly dull, and for refining the edge left by the coarse side.
This stone is similar to, but a bit more aggressive than the harder Norton 4 x 1 Round Combination India Stone.
Norton Item Number: JB64
Norton Part Number: 61463685435
Q. What are the grits of the Fine, Medium and Coarse in the Norton Crystolon stones?
A. The Coarse Crystolon is 120 grit, the Medium Crystolon is 180 grit and the Fine Crystolon is 320 grit. Please see our Norton Grit Chart for more information.