This Standard is intended to establish uniform practices for the measurement of master rings or ring gages using horizontal methods. The standard includes requirements for geometric qualities of master rings or ring gages, the important characteristics of the comparison equipment, environmental conditions, and the means to assure that measurements are made with an acceptable level of accuracy. This Standard does not include measurement methods for rings below 1 mm (0.040 in.). The measurement method on these very small rings should be agreed upon prior to manufacture or calibration between the manufacturer/laboratory and customer.