Bosch BL3139 12-Piece 3/16 In. x 2-3/16 In. Fractional Stubby Length Black Oxide Drill Bits Speed helix design for three times faster drilling than standard bits Last 50 percent longer than high-speed steel Easier drilling, reduced heat and extended drill bit life Available in jobber length, stubby length, extended length (aircraft), 1/2 In. reduced shank (Silver and Deming) For use in steel, copper, aluminum, brass, oak, maple, MDF, pine, PVC, polycarbonate, acrylic, ABS, nylon and composite materials