Double the ammunition on tap for your 9mm carbine! This magazine coupler is designed to fit 9mm Glock mags and fit in your AR-9, PC-9, FGC-9 or most any Glock mag fed PCC. Great for Home defense guns! Files include a version with a .375" gap between magazines, and .500" gap for use with flared mag wells or printed receivers. Enjoy! - Required hardware: 1 #8 screw 1.75" long, 1 #8 hex nut - Not recommended for firearms where the magazine is inserted into the grip (ie: glock pistols, sub 2000's, MPA Defenders) because the exterior magazine will obscure the grip.