Pipe Thread Ring Gauge, Long Form Calibration Certificate No, Material Tool Steel, Dimension Type Inch, Gauge Type Go/No-Go (Plus/Minus), Pitch Diameter 0.4903 (Go), 0.4859 (No-Go), Pitch Diameter - Go Member 0.4903 in, Pitch Diameter - No-Go Member 0.4859 in, Thread Class 2A, Thread Size 1/4 In.-18, Thread Type NPSM, Finish Uncoated, Hardness RC 60-62, Included Certification Certificate of Accuracy with NIST Traceability, Standards ASME B1.20.1, Tolerance Class X