Pipe Thread Ring Gauge Long Form Calibration Certificate No Material Tool Steel Dimension Type Inch Gauge Type Go (Plus) Pitch Diameter 0.6256 in Pitch Diameter - Go Member 0.6256 in Thread Class 2A Thread Size 3/8 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