100 Grit 4" Valve Grinder Stone. 100 Grit General Purpose Valve Grinder Stone. 4" Diameter, 1" overall thickness with a 1/2" offset. 5/8" Hole Diameter. Fits all older Sioux & Thor Valve Grinders that use a 4" Stone. Fits Black & Decker and Van Dorn A, B, C, LW, M, MW, N, NW, NWA, and NWB Valve Grinders.