Specification: Material: Steel Size: 3/4/5/6/8/10/12/14/16/18/20/22/25/26/28/30/32/35/38/50mm Quantity: 20 pcs Features: 1. This diamond coated core drill bit removes a complete circle from glass, tiles, marble, granite, ceramic or other. 2. Materials and only needs water for lubrication. 3. Always use lubrication (water), otherwise the diamond core drill will burn. 4. Works better with a electric drill 5. Start your hole diagonally, make a round trace and then hold drill straight. Package Included: 20 x Diamond coated drill bits