Threaded Ring Gauge, Long Form Calibration Certificate No, Material Tool Steel, Dimension Type Metric, Gauge Type No-Go (Minus), Pitch Diameter 18.164 mm, Pitch Diameter - No-Go Member 18.16 mm, Thread Class 6G, Thread Length 14.3 mm, Thread Size M20 x 2.50, Thread Type Metric, Compatible Holder Size 4T, Finish Uncoated, Gauge Design Adjustable, Hardness RC 60-62, Included Certification Certificate of Accuracy with NIST Traceability, Standards ASME B1.16M, Tolerance Class X