40/50 grit diamond , best on marble , granite and glass . For router stone with wood router . Use wet or dry . Water or other cooling agent is recommendedfor long life of the bit . Product Name : Diamond ProfileRouter Bit Material : King Kong Temple Cutting Radius : 8mm/ 5/16inch Shank Diameter : 12.7mm / 1/2inch Bearing Diameter : 13mm / 1/2inch Cutting Depth : 12.7mm / 1/2inch Overall Diameter : 31mm / 1 1/4inch Overall Length : 58mm / 2.3inch Color : GoldTone Weight : 86g Package Content : 3 x King Kong Temple Profile Router Bit Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.