I have the Marui GBB one, and it's great. In terms of size, trades, etc, that all seems correct; the added bit on the valve (embarrassed I don't remember what it's called...) of the mag is good as it allows the gun to fire easier. The stock on the TM one is also good, with little wobble, but apparently it can be broken by idiot midteens hyped up on pizza, coke, and OJ. I have never run out of gas before running out of ammo, but getting two fills out of a mag would be a stretch. I love mine, and used it some on Sunday, but my new PPSH had to take precedence.