Oil Seal Gun Drill bushings are intended to be used with gun-drilling machines. Using the positive sealing of the O-ring against the workpiece, your gun drilling machine will maintain the oil preasure required to continue optimum operating conditions. They are similar to Slip/Fixed renewable bushings, but with the drill bearing at the bushings head end. All American type GDS bushings are heat treated to RC 62-64 and ground concentric with .0002 T.I.R. These bushings are considered as special and not returnable. Prices available upon request.