Vermont Gage 371163050 1"-12 UNF 2A Go And No-Go Set Plug Gage Assembly Inch go and no-go plug gage set for inspecting pitch diameter and functional threads of internally threaded parts Made from Rockwell c scale (Rc) cold stabilized tool steel 60/62 for durability Supplied with a certificate of accuracy traceable to National Institute of Standards and Technology (NIST) Class X tolerance per ANSI B1.2 for unified inch screw threads Available in a range of sizes and thread fits for different applications