Pin Gauge Set,ZZ,Plus,.501 in-.625 in,125 pcs., Material Steel, Diameter Increment 0.001 in, Diameter Range 0.5010 in to 0.6250 in, Gauge Type Go (Plus), Overall Length 2 in, Tolerance +/-0.00020 in, Hardness RC 60-65, Included Certification Certificate of Accuracy, Standards NIST, Dimension Type Inch