Quick adjustment wrench head with serrated teeth for firm grip on even the most rounded fixings. 3/8" square drive & square hole allowing it to be used with power bars, ratchets & extension bars. Simple. pull back action allows a quick and firm grip to fixings of any size from 8mm up to 17mm. For use on all types of bolts, including Single Hex (6pt), Bi-Hex (12pt), Star/Torx, Spline, Square etc. Manufactured from chrome vanadium for strength. 1/2"D adjustable crows foot wrench head available, please see Laser Part No. 8216.