||I bough 5 of these for my Echo 1 Stag arms m4 and I was slightly disappointed right off the back. First off, these don't fit Echo 1 despite what the description says. The problem is that the mag release/catch doesn't fit into the slot on the side of the mag. So I had to grind the top border of this slot to make it fit properly. It was a little annoying having to modify the mags, but after doing that these mags sit firmly in place and don't wobble at all. I mean NO WOBBLE.
As far as feeding, they do a really good job from what I've tested so far. My only beef with it is that they don't feed the last bb which is a little annoying but not the end of the world.
The aluminum that this mag is made of is fairly durable and can withstand being dropped on a hard surface floor, although I wouldn't make a habit of doing so. ;) The paint job of these mags wears off fairly easily, which for some might be a con, but I like my gear to look rugged and worn, so for me that's just what the doctor ordered.
All in all, I give this mag a 4/5. I would have given this a 3/5 for the lack of compatibility, but that's more the product of bad product description, not the actual construction.
Bad product description (not really against the mag itself)
Paint job wears off easily (not really a con for me)
fails to load last bb
Rating: [4 of 5 Stars!]