Similar to the G3 Gun Holster the G3 Extra Mag carrier is a uniquely designed holster to comfortably conceal carry your extra magazine(s) with nearly any outfit for any situation. Will Double Stack Mags work? * Yes, any standard size double-stack magazine will fit as well. Will Extended Mags work? * Typically yes up to about 16-22 rounds depending on the caliber. Any extra extended magazines with 25-30 rounds usually will not fit in th