I got one of these a while back and at the time i hadn't realized it was for the newer style PMAG, luckily i had several of both versions so no loss to me. This is molded to fit the newer PMAGs and it really only seats properly at the bottom of the mag (as opposed to the middle which you can do, but i don't think it's as stable). It also works with the T-mags which are just clear versions.
Until you get it on there, this thing goes slipping and sliding and can't seem to get a grip. but once you get it in position and tightened down I swear the mags will snap in two before they wiggle or come loose from this clamp!
It's a specialised bit of accessory but it does exactly what is advertised and it does it (rarely do i say this) PERFECTLY!
Holds the mags tight as can be done without risking damage to the mag shell
Proprietary to only the one kind of mags
really only has one link configuration (only a con if you don't like that configuration
It's still clamped mags which means dumping it on the go can be a pain
Rating: [5 of 5 Stars!]