The Klein Tools 2-in-1 Impact Sockets, Nos. 66004 and 66001, offer two coaxial spring-loaded 3/4" and 9/16" hex sockets in one tool. 66004 features a high torque, 6-point design that helps reduce round-off with contacts to flat sides of hex fasteners. 66001 features a high torque, 12-point design is easy to position and works with square fasteners. Both sockets are engineered for use with impact drivers.