This fiveseven 10rd mag extension is the ultimate upgrade to your 5.7×28 pistol.Installation takes only seconds and does not permanently alter factory magazine.Chrome silicon spring is salt water-resistant and will not take a set. Caliber: 5.7x28mm Capacity: 10rd Finish: Black Model: FiveSeven Type: Magazine Extension Model Fit: Five-seveN Brand Fit: FN Capacity: 10
