Package Includes: as images show, 501519 Aftermarket Piston Driver 1 pcs. Compatible With: Paslode F-350S with O-Ring 502104 Nailers Parts. Heat treated tool steel 6150 - Rockwell hardness 50-52, Aerospace grade #2024 Aluminum piston, Mechanically locked piston driver interface. These parts install quickly to make your nailer work like new again. A brand-new, unused, unopened, undamaged item in its original packaging.