I bought this to store a folding MK18, which it fits quite well. I'm selling that particular AR, so I don't really need the backpack anymore. It's in perfect shape. It held a gun in the trunk of a car from time to time.
It's a very nice back, low profile, doesn't scream "look at me" the way that so many other packs do. Don't know the specs on it, I'm sure they're widely available online.