HiKOKI 377103 Piston Bumper HNBR for compatible HiKOKI cordless nailers. This replacement piston bumper is designed to cushion the piston during operation and is suitable for replacing a worn, damaged or deteriorated original component. Manufactured to the correct specifications for precise fit and reliable operation. Part 377103 replaces the previous HiKOKI part number 372317.