Vltor RE-1 Mil-Spec Five-Position Carbine / Collapsible Receiver Extension (M4 / AR15 Weapon Series) Vltor Carbine/collapsible Buttstocks will only fit MilSpec Receiver Extensions, such as Colt and Vltor. The Vltor RE-1 Receiver Extension tube for M4 and CAR15 series of carbines. The RE-1 is constructed from impact extruded 7075-T6 aluminum and meets all requirements of the military specification. We are sure that the RE-1 is the best receiver extension tube on the market. We offer a 5-position Receiver Extension for both the M4 and CAR15 weapon series (Model# RE-1) as well as one for the Armalite AR10TMcarbine and rifle (Model# RE-10). The RE-10 extension will only work when using the Armalite AR-10B Operation Spring, part# EA1095 and AR10 Carbine Buffer part# EC0120. The receiver extension has a MilSpec outer profile and will only accept Colt or Vltor dimensioned buttstocks.
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