Drive five types of tamper-resistant screws in a range of sizes with the TEKTON 33-pc. Security Screwdriver Bit Set. The tip of each bit is precision milled for an exact fit in screw heads. The bits are made of premium chrome vanadium steel with a universally sized 1/4-inch hex shank that can be used with power drivers or screw guns. Bits and bit holder pack neatly and efficiently into a pocket-sized organizer