Black Proto Matrix Rail, Black NDZ Slik Trigger, Black NDZ Back Cap, Viewloader Evolution II w/ Z Board, Pure Energy N2
Does Not Strip
Does Not Come Loose
Aluminum-The stock back cap is polymer, and this is aluminum. It is MUCH more durable, and the weight is unnoticeable.
Does Not Strip-The stock back cap strips extremely easy, but this one you could tighten as much as you want and it will never strip.
Does Not Come Loose-Since the stock back cap strips so easily, you can not tighten it too much, and it comes loose after shooting a hopper of paint. Since this one can be tightened as much as you desire, it will NEVER come loose.
It may cost $25 for something as simple as a back cap, but you will never have to worry about stripping it or it coming loose mid game. It is 100 times better than the stock one, and I would not return it for the $25.