BLACKHAWK! describes this item as follows:
Our magazine pouches have a built-in tension spring, to hold your magazine in place until you need it and to allow the use of a variety of magazines in each pouch. The most interesting thing about our magazine pouches is that the unique belt clip can be removed and they can be placed side by side on our Dual Rail Accessory Platform, for those wanting a double magazine pouch, on the same carrier. Or, they can be placed beside one of our light carriers, for a combo light/mag carrier.