1. : diamond grinding for machining of glass: glass thickness, jade, jade, agate, pearls and other building materials. 2. the : electric drill speed 3600 rpm, bench drill and machine speed in 6000 ~ 10000. The water must be so as to achieve the best effect. 3. About how to the explanation: if the material thickness of 8mm, the appropriate 8mm diamond grinding . Specification: Shaft diameter: 6mm Outer diameter: 20mm Grit:150 Width: 5mm Colour: As Shown Material: electroplating emery Package Contents: 1 x Diamond grinding Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.