Stanley Proto J6018CXCERT 3/4-Inch Drive Ratcheting Head Micrometer Torque Wrench, 60-300-Feet Pound Calibrated to +/- 3% in clockwise direction and +/- 6% in counter clockwise direction Calibration is accomplished by mechanical loading each wrench in a horizontal position Certification documents traceable to N.I.S.T. (National Institute of Standards and Technology) Manufactured to meet precision/highly accurate applications such as military and aerospace