The Atlas Gunworks Classic 2011/1911 Double Stack Magazines are available in 17 and 20-round configurations. We recommend classic magazines to shooters looking for a tough magazine that feeds awesome and locks back reliably in most modular 1911 double stack and 2011 style pistols, including Staccato and Springfield Prodigy. Features Caliber: 9mm Capacity: 20 Rounds Tube: 140mm Stainless Steel Follower: Lockback Spring: + 18% Basepad: Aluminum, prevents over-insertion 18345-51975