Calibrated to ± 4% of torque reading, clockwise at 20% to 100% of full scale. 1/4" square to 1/4" hex adapter included for use with insert bits. Industrial heavy-duty design. Aircraft grade aluminum. Aircraft quality spring. Positive self locking lock ring. Floating three-point reaction for repeatability. Laser marked easy-to-read scale. N.I.S.T. Meets or exceeds ASME B107.14M.