The CQC 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 the Dual Rail Accessory Platform (sold separately). The case can also be placed next to one of the light carriers for a combo light/mag carrier. FeaturesFeatures a built-in tension spring to securely hold magazines of various sizesRemove the belt clip and place two Single Mag Cases side-by-side on Dual Rail Accessory PlatformFits 9mm/.40 cal