For gaging standard pipe and pipe fitting! Use Vermont Gage pipe thread rings to check tapered and straight internal pipe threads. Perfect for inspecting standard pipe and pipe fittings. Vermont Gage pipe threads are made to precise class X tolerance and come with Certificate of Accuracy. The NPT and NPTF (Dryseal) series includes standard tapered pitch diameters. The NPSM series includes standard straight pitch diameters. Class X. NIST Traceable. Tool Steel; 60/62 Rc/ (Cold Stabilized). Certificate of accuracy included.