Magpul sand gen M3 5.56/.223 30 round window P-MAG.
Newest, third generation MAG556-SND Pmag includes a dust cover and features lots of updates, like skinny a profile floorplate to fit better in pouches, rear tab to prevent over insertion of the mag, and an even more durable polymer. The new sand colored PMAG can be dyed. http://www.youtube.com/watch?v=En9PF6PtFP8
It will work in just about every rifle that uses standard 5.56/.223 AR-15 type magazines.