A magnetic insert makes screws “stick” to the bit. Use only with 1" long “insert” style bits. Inadvertent use with a “Ball Detent” style bit makes it almost impossible to remove the bit – believe me! The wire ring grips the bit quite firmly, so you may need to use a pair of pliers to remove even the 1" bits. Hex shank fits Jacobs® style 3 jaw drill chucks, most power screw drivers, and the Insty-Bit system Quik Change chuck adapters. Bit not included.