A SIGTEC LOCKNUT has two parts per set. The tapered-washer tighten up the thread. It gives a strong locking power to the nut, securely tighten against vibration, shock and temperature.No special tools are required. Adequate torque control is easily achieved. Just assemble as a conventional nut.Optimizing cost saving, lobar cost and good workability. Available Sizes Metric Sizes M8