G2745 Drill Bushing Bushing Type Head Press Fit H Inside Dia 4.5mm Outside Dia 5/16 In Inside Dia Tolerance +.0001- +.0004 In Outside Dia Tolerance +0.0016 - +0.0013 In Concentricity Tolerance .0003 In T.I.R. Max Overall Length 1/4 In Material 52100 Thru Hardened Finish STEEL Drill Size 4.5mm Hardness RC 62-64