US PRO 6 Piece 1/2" Drive Spline Impact Socket Bits Set. Manufactured from Chrome Molybdenum Alloy Steel with a black phosphate finish hardened and tempered these spline bits withstand very high speed power tools. Each large spline bit is 78mm long giving you greater access too hard to reach places. The short spline bits are 40mm long giving you more power where it's needed. 6 piece 1/2" spline bits. Professional quality. Chrome Molybdenum Alloy Steel. Black phosphate finish. DIN 3121. Hardened and tempered. True impact. 1/2" inch drive. Blow moulded case.