I put them on my WE M4 mags. They needed a bit of fitting (filing the plastic plate just a bit so there'd be enough room to slide the plate on). The rubber ones I got from Airsoftparts.ca didn't have a hole in them so I could use the AI gas adaptor with the duster extension to fill my mags. I used a 1/4" drill bit and drilled through the rubber plate, the metal underlying plate and the plastic insert. Works just fine.
* note: the ones on the site now seem to have the hole pre-drilled
http://www.airsoftparts.ca/store2/in...oducts_id=1868
I did need to bend/nudge the baseplate tabs of the mag up a bit to get everything in...then bend them back down afterwards. Just a bit, nothing major.
A buddy mine has hard plastic ranger plates on his...I think they came with the hole in them (note...see Sinn's post, I guess they don't). I'm pretty sure they were "clone" ones from somewhere.
So the answer is yes...if they fit and come with the hole you're all set. If the hole isn't there...just measure up where it should be and drill one.