The BLACKHAWK CQC double stack Mag case 9mm/.40 Cal. Is a carbon-fiber composite magazine pouch with a built-in tension spring which will hold your magazine in place until you need it and will allow the use of a variety of magazines in each pouch. The BLACKHAWK CQC double stack Mag pouch has a proprietary belt clip that functions as a clip-on design but has the stability of a belt loop. The stability of the BLACKHAWK CQC double stack Mag case is due to the hold and strength from the aggressive Talon and special carbon-fiber material. The single stack magazine pouch works with all caliber single column mags, from 9mm to 45 caliber. These double stack magazine pouches will take all 9mm and 40 caliber staggered column magazines, including polymer-body designs. The most interesting thing about BLACKHAWK CQC carbon fiber Mag pouches is that the unique belt clip can be removed and they can be placed side by side on the BLACKHAWK dual rail accessory platform. The BLACKHAWK CQC CF Mag pouch 9mm/.40 Cal. - double stack can also be placed beside one of blackhawk's light Carriers, for a Combo light/Mag carrier. BLACKHAWK designed these Mag cases to give the user choices, and not limits..