For milling machine、 lathe、 drilling machine、 wood working machine.The shank with scrw can be tight and flex for you.Should work with power drill、 here is not included.Specification:Capacity:0.6-6.5mmMount Thread:3/8-24UNFInterior Hole Diameter 6mm/ 0.24"Exterior Hole Diameter Small: 30mm/ 1.2"、 Big: 23mm/ 0.9"Total Height 4.7cm/ 1.85"Chuck Key 55 x 35mm/ 2.2" x 1.4" (L*W)Main Material: MetalColor Black、 Silver TonePackage Included:1 x 0.6-6.5mm Drill Chuck1 x Chuck Key1 x 1/4" hex shaft