Superior Parts DB83-01C is a NR83A / A2 – Carbide Driver & Bumper Kit which includes SP 877-323C piston driver & SP 878-303 piston bumper.SP 877-323 Piston Driver: This is a generic replacement driver with o-ring for the Hitachi NR83A, NR83A2, NR83A2(S) framing guns. This comes with a patent pending locking mechanism which will not allow the driver to unscrew from the piston. Aluminum is crimped into the unilok grooves of the shaft to prevent unscrewing. Guaranteed never to unscrew.SP 878-303 Piston Bumper: Precision machined, virgin high density yellow color plastic framer bumper.