10/30 Magpul 5.56 Gen M3 front riveted P-Mag. A 1/8" rivet has been installed into the front of the magazine to block the follower and limit the capacity of the magazine to 10 rounds. The third generation MAG557-BLK P-Mag comes with a dust cover and 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.