Drill Bushing Bushing Type HL Head Liner Inside Dia 3/4 In Outside Dia 1 In Inside Dia Tolerance +0.0003 +0.0006 In Outside Dia Tolerance +0.0015 +0.0018 In Concentricity Tolerance .0005 In T.I.R Max Overall Length 1-3/8 In Material 52137 Thur Hardened Drill Size 3/4 In Hardness RC 62-64