Dual scale, calibrated dual direction. Positive lock with spring loaded pull down lock ring. Fast, accurate and easy to set. Easy-to-read laser marked scales. Most feature quick release buttons which provide good socket retention as well as easy socket removal. Accuracy: 4% CW 6% CCW of indicated value, CW, from 2% to 1% of full scale. Accuracy: 4% CW 6% CCW of indicated value, CW, from 2% to 1% of full scale. Meets or exceeds ASME standards, ISO 6789 standards. Individually serialized with matching certificate of calibration traceable to N.I.S.T