The Umarex GLOCK G18 Green Gas 50rd extended spare airsoft magazine by VFC is made from heavyweight aluminum, giving a hefty feel to the G18 airsoft pistol. The extended GLOCK magazine offers over twice the shots as regular GBB magazines. This green gas Umarex magazine has a high-efficiency internal gas system providing excellent FPS output and reinforced valves and seals for optimal gas retention. We recommend using Valken Green Gas with this gas pistol magazine.