Thread gages inspect the pitch diameter and the functional thread for both internal and external threaded products. The thread gages listed are made to Class X tolerances per ANSI B1.2 (Unified inch screw threads). All thread gages are supplied with a Certificate of Accuracy. Work plugs are stocked in 2B & 3B (inch) classes of fit. Stocked work plugs are chrome plated. All thread gages are marked with nominal size, threads per inch (inch), class of fit, and pitch diameters.