Patented bit holding system forces bit surface to opposing side for maximum retention. Chrome sockets; heat treated for durability and service ability. S2 and Alloy steel bits. Packaged in patented impact resistant "Slide Rail" System for ease in socket storage10 Piece Metric Hex Bit Set (3/8" and 1/2" Drive) includes 4, 5, 6, 7, 8, 9, 10, 12, 14, and 17mm Sockets. Packaged on a clip rail.