0.5101"-0.8250" (12.96Mm-20.95Mm) Carbide Class Xx Master Ring Gage. Nist Traceable. C-2 Tungsten Carbide; 90/92 Hra. Round Within 1/2 Of Tolerance. Marked With Size And Direction Of Tolerance. Certificate Of Accuracy Included. Custom Carbide Ring Gage. High Wear Resistance For Extended Gage Life. Perfect For Use As Masters For Bore Gages And Internal Micrometers. Use Vermont Gage Ring Gages To Efficiently Inspect External Dimensions Of Manufactured Parts. With A Go And Nogo Ring, An Inspector Can Quickly Pass/Fail Parts Without Taking Time Consuming Readings From An Indicator. Available In Master (Bi-Lateral Tolerance), Go (Minus Tolerance) Or No-Go (Plus Tolerance). Nist Traceable. Certificate Of Accuracy Included. Vermont Gage Usa Part #233106310. At Checkout, In The 'Additional Instructions' Field, Specify The Ring Gage Inside Diameter Within The Range Specified.