Chiappa Firearms 500095 M4-22 AR-15 Rifle Upper Conversion Kit GEN-II 22LR The Gen-II Pro Series Rifle upper is an evolution of the M4 model adding an 11.8" free float aluminium forend with 8 position Picatinny rail. All other characteristics remain unvaried: 18.5" heavy match parkerized barrel steel bolt Mil-Spec components. Fully functional with select fire lowers