Zeluga 878-179 Piston Bumper NV45AA, NV45AB, NV45AB2M Pneumatic Coil Roofing Nailer . Made from durable rubber and loacted inside the head of the nailer. It absorbs the shock and provide cushioning when piston cycles back after driving a nail. It also prevents metal-on-metal contact that could damage the tool. The cushioning the piston impact it reduces the noise generated during operation. Well functioning bumper ensures the nailer operates efficiently and smooth with consistent driving force for each nail.