I have a VFC E Series M4, and I have a few of the tan version mags. (same everything different color.) I bought them off another website but this is about the same price everywhere, so I suppose it just comes to preference. I also have a friend who has the same gun as I do and uses these black elite force pack, and they were a little shaky in his gun but it was an easy, inexpensive fix with some electrical tape or velcro tape on the edges of the mags so that they'd stay nice and tug. I couldn't (for some odd reason) fit the velcro taped mags in my gun (too tight) so the size just depends on the gun. Overall these work extremely well and just look sweet in just about any m4.
(these DO fit in most M4's, but you will have to decide how tight you need to make them for them to not shake, which with some they shake just a little and with others, none at all. again, that can be an inexpensive fix or cost nothing at all. just use black electrical tape or (soft side) velcro tape, and apply however much your gun requires.)
-They look so awesome, especially in tan.
-Great Price and totally worth it
-Have great feeding
-Made of durable, abs plastic.
-Don't take long to break in, they hold close the amount described even right out of the box!
Great product, Great price!
None really, just a peice of advice-to help them last long and keep their amazing quality, apply some airsoft lubricant in the feed-mouth every 800+ rounds.