Pin Gauge Set ZZ Plus .251 in-.5 in 250 pcs. Material Steel Diameter Increment 0.001 in Diameter Range 0.2510 in to 0.5000 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