1.00" ‐ 6.00" diameter in 1.00" increments for outside jaws and 1/2" to 4 1/2" inside jaws . Case hardened, stabilized, ground and lapped to +/‐.0002". Vernier masters are used to calibrate vernier calipers. The master is superior to gage blocks calibration because they do not require block stacks so it is much faster to inspect the linear range of the tool. In addition they indicate wear on the caliper anvils because both the I.D. and O.D. jaws are inspected wihout additional setup.