The heavy duty AV-4 is a must-have tool for every mechanics workbench Designed to securely hold 5/16 inch to 9/16 inch axles for easy wheel-hub & pedal adjustments A choice of three precision-machined openings allow you to grip axles & tighten the tool in a workbench vice Aluminium jaws prevent you from damaging ultra fine axle threads Bridge springs keep the jaws properly aligned & allow the tool to open automatically when the vice is opened