Fast adjustment directly on the work piece eliminates time-consuming test adjusting of the correct opening size. Just position the upper jaw to the work piece, push button on pliers and move close the lower jaw. Once adjusted the pliers self-lock on pipes and nuts with no slipping. Optimized shape jaw will grip round, square and hex shaped material. The box joint design provides high stability because of the double guide.Fast Adjustment Directly on the Work Piece, Just Position the Upper Jaw to the Work Piece , Push Button and Move Close the Lower Jaw. Gripping Surfaces with Special Hardened Teeth, Teeth Hardness Approximately 61 HRC Provides Low Wear and a Secure Grip