877-323 Piston Driver: Aluminum is crimped into the unilok grooves of the shaft to prevent unscrewing. Hardened steel lock tite and micro-mechanically locked piston driver interface. Guaranteed never to unscrew.nail gun parts original
878-303 Piston Bumper: Precision machined, high density yellow color plastic framer bumper.
Driver & Bumper Kit - Pack of 6 which includes 3pc 877-323 piston driver & 3pc 878-303 piston bumper.