Automatically fits 15 different nut and screw sizes. Hex head adjusts to the proper size as you turn it. Will drive or loosen hex nuts from 1/4in (6.4 mm) to 7/16in (11.1 mm)- hex-head screws from No. 6 to 1/4in (6.4 mm)- and socket-head cap screws from No. 8 to 5/16in (7.9 mm).