Is your DeWalt nailer leaking air or not firing right? This repair kit might be just what you need to get it back in action. It includes two key parts: the main Trigger Valve Assembly (part # 647956-00, also replaces 641011-00, 647620-00) AND a D51844 O-Ring rebuild kit. This combo is designed to fix common issues on a bunch of DeWalt pneumatic nailers and staplers. It fits models like the D51844 and D51822 framing nailers, D51256 and D51275 finish nailers, D51321 roofing nailer, D51430/D51431 staplers, and many more (check the full list in the description to be sure). The O-ring kit is universal for Types 1-5. The trigger valve assembly is the heart of the firing mechanism. If you're handy and comfortable taking your tool apart for maintenance, this affordable kit can save you a fortune compared to buying a whole new nailer or sending it out for service. Get your favorite tool driving nails smoothly again!