CMC Triggers Upper Receiver Parts Kit Features The CMC Triggers Upper Receiver Parts Kit provides everything needed to complete a mil-spec AR-15 dust cover also called a trapdoor assembly including the door itself the spring the rod and the retaining C-clip. Keeping this assembly intact and functional protects the upper receiver s internals from dirt sand and debris when the rifle is stored or carried without a round chambered. The rod is machined from stainless steel and finished in black nitride a step up from the plain steel rods found on many factory and aftermarket kits that tend to rust with exposure to moisture. This finish combination extends the service life of the part considerably compared to untreated steel. Because the kit is built to mil-spec dimensions it installs on any standard AR-15 upper receiver without fitting or modification. Replacing a missing or damaged dust cover is a simple task with all the needed components included in a single kit rather than sourcing individual parts separately. CMC Triggers is better known for its AR-15 trigger groups and the same attention to manufacturing tolerance carries over into this smaller but essential upper receiver component. For an AR-15 owner needing a complete corrosion resistant dust cover assembly this CMC Triggers kit is a straightforward fix available for sale at GrabAGun. CMC Triggers Upper Receiver Parts Kit Specifications Manufacturer: CMC Triggers Model: Upper Receiver Parts Kit Type: Kit Color: Black Compatible Hosts: AR-15 Material: Steel Available At: GrabAGun