Vermont Standard Thread Ring Gage Set, GO/NOGO, 3/8-28 UNVermont Standard Thread Ring Gage Set, GO NOGO, Vermont's Thread Gages allow you to inspect the pitch diameter for threaded products. All stock Thread Ring Gages are made to Class X tolerances per ASME B1. 2 (Unified Inch Screw Threads). A Certificate of Accuracy is included with each gage. Available in 2A or 3A, and each Thread Ring Gage is marked with nominal size, threads per inch, class of fit and pitch diameters. Features include 3 8 28 UN