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 assembly kit (HY00000956) contains the parts needed for piston assembly, including the seal ring, O-Ring, and driver complete. 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.