Well, I don't know much about these fancy deals... but it has a little Phillips head screw in the back holding it on. What's with that? Theres a rubber like collar at the back of the slug. That's the dark area you see. I always just shot some Remington or something but thought I'd try these. They seem more accurate so I bought some more. The only shells the gun has shot in the past 3 or 4 years is checking the zero.