Anything that makes use of STANAG mags is 5.56x45mm, so that's your M4s, M16s, L85s, Tavors, there's quite a few options.
But mag pulls will only fit on STANAG type mags as far as I know, no good for other 5.56 rifles like G36s or Sigs, though there's also the 7.26 mag pulls for M14s and SCAR H variants etc.
I can't recommend them personally, but I have 12 mags on me when I play and I manage perfectly fine without them, I tend to carry my mags facing up, you'd have to have them upside down with these attached.
If you're a hi-cap user then they might get in the way of your mag winder as well.
Not sure about the branding of them, I've only ever seen them sold at Patrol Base (not that I've actually done a search) and they're about £3.50 per unit, which is way too expensive for me to buy 12 of them.