Kobalt 42-Piece Impact Screwdriver Bit Set Includes the most popular screwdriver and nut driver sizes Black oxide finish resists corrosion and extends tool life Heat treated hardened S2 steel for maximum durability For use w/ impact drill/drivers & compatible w/ the Kobalt SpeedFit 2in1 quick-change connector 1/4" and 3/8 Hex-to Square socket adapters