hi cy,
i have one on my DPMS, it came with it already attached. the tube is nice, but, i didn't like the feel of the rails. so, i put the guard rail potectors on the tube and it feels much better.
lynn
this is what i like to tell shooters that want to go up in class: "you really don't want to go up in a class until you can consistently win your class in a major match."