This is a Magpul Industries Magazine Accessory known as the Ranger Floorplate chambered in 223 Remington, model MAG020-FDE.
The Magpul Ranger Plate is a floorplate replacement for current issue aluminum USGI 30-round magazines that incorporates an integral loop" floorplate lock" and mag identifier. When installed on the base of a magazine" the Ranger Plate provides unsurpassed speed and controllability during high stress" tactical magazine changes. Loop is made of pliable Santoprene rubber overmolded onto a stainless steel plate. Patented design based upon the tried and true para-cord loops and duct-tape tabs currently in use with special warfare units worldwide.
Features:
Floorplate replacement for current issue aluminum USGI 30RD mags
Provided improved speed and controllability during tactical mag changes