These will fit perfectly for 2x MAG magazines clamped together. Sadly they're china quality, and the velcro will only last you for aprox. 1 year at best. Oh and you need to remove the wall inside by cutting the stiches. Shouldn't take long, but I'd rather pay some extra $$ for something like these:
http://www.lapolicegear.com/blackhaw...mag-pouch.html
http://www.kaboodle.com/reviews/blac...iple-m16-pouch
The foregrip RIS I got didn't have much more space then the original foregrip. The compartment is slightly less curved at the upper part. You'll still fit batteries like the 7.4v lipos made for Lama helos. If I get my hands on two, I'll hook them up in parallel and see if they can deliver enough juice. I bought one Mystery 7.4v 900mAh 20C lipo, and it absolutely s*cked! I'm guessing it's peak discharge-rate is barely 20C. For those that doesn't wanna mess around with lipos like that, there are better options that'll absolutely fit inside:
http://www.khmountain.com/airsoft/pr...oducts_id=1171
http://www.khmountain.com/airsoft/pr...oducts_id=1177