Positive locking mechanism dial and lock-in the desired torque. When desired torque is reached, there is an audible 'click' and a "feel impulse", and the wrench re-sets automatically. Designed to retain calibration for 30,000 cycles under normal use. Calibrated to /- 4% of torque reading clockwise and /- 6% anti-clockwise at 20 to 100% of full scale. Certified wrenches to /- 2% are available upon request. Knurled steel handle for durability and a non-slip grip. Packaged in blow moulded boxes for protection and easy storage.