Great cover, highly recommend !!
This is a standard trapdoor assembly, no frills to this part, just as it should be. The one place some trapdoors actually do seem to vary is in the strength of the spring tensioning the ball detent on the trapdoor itself, some can be too stiff and cause the trapdoor to be excessively hard to open and close. The examples I have seen from KAK have moderate tension on them and open and close smoothly, but still positively lock closed. Once again, just as it should. Kit comes with the trapdoor, the spring, the pin, and the pin retaining ring. Look carefully when opening as retaining rings are small and can be stuck to the trapdoor itself or bag and can easily be lost after removing the parts from the bag. Item is a must for finishing upper builds, but don't miss what I missed and if you're finishing off uppers be aware KAK also sells full upper completion kits (trapdoor and forward assist assembly) for a few bucks cheaper than buying the parts individually.