With the Mitutoyo 177-298 steel setting ring, you can quickly and accurately zero-set and calibrate internal measuring tools such as bore gages, inside micrometers, and three-point internal micrometers. Made from hardened steel, this setting ring delivers exceptional dimensional stability and wear resistance, ensuring dependable, repeatable measurement results in the workshop or quality control lab. Thanks to the clearly marked actual inside diameter around the nominal 125 mm size, you perform reference calibration with complete confidence and eliminate measurement errors.