Our Single Mag Cases feature a built-in tension spring to securely hold magazines of various sizes. For two magazines on the same carrier, you can remove the belt clip and place two Single Mag Cases side-by-side on our Dual Rail Accessory Platform (sold separately). The case can also be placed next to one of our light carriers for a combo light/mag carrier. • Features a built-in tension spring to securely hold magazines ofvarious sizes• Remove the belt clip and place two Single Mag Cases side-by-side on Dual Rail Accessory Platform• Fits 9mm/.40 cal/.45 cal/10mm/.357 Sig