Lenox Leader Self-Feed Bits - Designed for Continuous Self-feeding. FAST CUTTING - Precision ground teeth and outside diameter threads maximize tool performance. INCREASED CAPABILITIES - Extra long to cut through 4x4 with no extension required. RESHARPENABLE - Easily resharpened with Lenox Slim Taper File (32510-STF). Replaceable lead screws. 4-1/2" shank length, 5-1/2" overall length, fits 1/2" drill chuck and larger. Shank indentations for extension bar set screws.