Drill Bit Diameter: Multi Size. Material: Carbide Tipped. Number in Set: 3 pc. Bearing Diameter: 1/2 in. Shank Diameter: 1/4 in. Application: Wood. Maximum Speed: 27,000 rpm. Includes: 1/4" straight bit, 1/2" dovetail bit, 9/16" dovetail bit, and storage case. Designed with a special control feed shoulder to help prevent overfeed.