The Senco EA0392 Piston/Driver Assembly W/O-Ring helps transfer driving force to fasteners in compatible pneumatic nailer equipment. This replacement assembly moves within the tool's cylinder and drives the fastener when the nailer is activated. A properly functioning piston and driver support consistent fastening, smooth cycling, and dependable tool operation. Replacing a worn or dam... https://www.wholetoolbox.com/senco-ea0392-piston-driver-assembly-w-o-ring/EA0392.html