I have been very impressed with this AEG, for it's price it even knocks out some higher end M4 models. From what I read it's 100% upgradable, and fits a lot of external parts such as Daniel Defense. Now that I have upgraded several internal parts, I would like to add a RIS rail. The only thing is I'm unsure which to get. I have been looking at the Madbull Daniel Defense 7"
http://madbull.com/catalog/index.php...roducts_id=271
but will I need an Omega version due to having a delta ring?
http://madbull.com/catalog/index.php...roducts_id=226
And is 7" even the right length for an M4, because if I measure from delta ring to the end cap, I get less than 7".