FAB Defense M4 Polymer Magazine Coupler Black. These Gun Accessories byFAB Defense space the magazines perfectly for proper function and will not change position. The FAB Defense AR-15 Modular Magazine Coupler sits M16 magazines and Galil 5.56 magazines. These Gun Accessories are made with a Mil-Spec reinforced polymer material that is guaranteed to stand the test of time more efficiently that inferior models. For a great way to quickly reload your tactical rifle choose the FAB Defense Magazine AR15 Modular Coupler Holster. Specifications for FAB Defense Modular AR15 Magazine Couplers: Manufacturer: FAB Defense Gun Model: AR-15 Features of FAB Defense Tactical Rifle Modular Magazine Coupler: Couples magazines Fast initial reloads Spaced and staggered perfectly Can't change position Mil-Spec Reinforced Polymer Fits M16 M4 AR15 Galil 5.56 Magazines Package Contents: FAB Defense Modular M16 M4 AR15 Magazing Coupler TZ-M4 What firearm models does the manufacturer say FAB Defense Modular AR15 Magazine Couplers is compatible with? The manufacturer says that FAB Defense Modular AR15 Magazine Couplers is compatible with AR-15FX-TZM4: FAB Defense Magazine Couplers - AR15 Modular