Third generation MAG557-SND P-MAG with dust cover. The newest P-Mag features lots of updates, like skinny profile floorplates to fit better in pouches, rear tabs 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
These will work in just about every rifle that use standard 5.56/.223 AR-15 type magazines.