Part Number: 901901 2 Pack. 901901 Piston Bumper fit for Porter Cable FR350 FC350. This part acts as a cushion when the piston/driver retracts back into the cylinder after being fired. This Piston Bumper is located Cylinder Cap of nail guns. Fit For FC350 Type 1, FC350 Type 2, FC350 Type 3, Fit For FR350 Type 1, FR350 Type 2, FR350 Type 3, Does NOT WORK for the FR350A model. A brand-new, unused, unopened, undamaged item in its original packaging.