TEKTON 3-PC. IMPACT UNIVERSAL JOINT SET features: Drop Forged, Heat Treated Chrome Vanadium Steel, Oil-Quenched, Black-Oxide Finish for Durability, Holes on Universal Joints for Locking onto Drive Tang, Spring-Loaded Ball Bearings Hold Sockets Securely, Specially Designed for Use with Air Tools, Ball/Swivel Action Universal Joints Gives Sockets Access in Tight Areas, 1-pc. 1/4"-Drive, 1-pc. 3/8"-Drive, 1-pc. 1/2"-Drive.