Air Hard Drill Rod Steel Material Fractional Size 21/32 In. Decimal Equivalent 0.6562 In. Dia Tolerance +/-.001 In. Finish 20 RMS Max Length 36 In. Length Tolerance +.125 In./-.000 In. Hardness Scale 241 BHN Max Grade A2 Standards UNS T30102 SAE J437 ASTM A-681-94 FEDERAL QQT-570 REV C