Keep your Makita 21° full Round Head 3-1/2” framing nailer (AN924, sold separately) operating at optimum efficiency with the comprehensive replacement Kit. The piston bumper kit (HY00000957) contains the parts needed for replacing the piston bumpers, including the seal ring and piston bumpers a and B. Each part is made of high quality materials for long lasting performance. The AN924 is engineered for a range of applications including framing walls, floors and roofs, as well as construction of roof and floor decking, floor and wall sheathing/Siding, and sub-flooring.