10 Pc. Triple Square Spline Bit Socket Set. Includes triple square spline bit sockets. Sockets are made from heat treated chrome vanadium steel for strength & durability. (10) Triple Square Spline Bit Sockets: ATD-232 - M4 1/4" Drive ATD-233 - M5 1/4" Drive ATD-234 - M6 1/4" Drive ATD-235 - M8 3/8" Drive ATD-236 - M9 3/8" Drive ATD-237 - M10 3/8" Drive ATD-238 - M12 3/8" Drive ATD-239 - M14 3/8" Drive Tamperproof ATD-241 - M16 1/2" Drive Tamperproof ATD-242 - M18 1/2" Drive Tamperproof