(13) Ribe Bit Sockets: M4 1/4 Drive (ATD-255) M5 1/4 Drive (ATD-256) M6 1/4 Drive (ATD-257) M7 3/8 Drive (ATD-258) M8 3/8 Drive (ATD-259) M9 3/8 Drive (ATD-261) M10 3/8 Drive (ATD-262) M11 3/8 Drive (ATD-263) M12 3/8 Drive (ATD-264) M13 1/2 Drive (ATD-265) M14 1/2 Drive (ATD-266) M15 1/2 Drive (ATD-267) M16 1/2 Drive (ATD-268) Includes 6-lobe ribe/polydrive bit sockets Bits are made from S2 steel to meet or exceed torque specifications Sockets are made from heat treated chrome vanadium steel for strength & durability .