 Most of the rifle's receiver is constructed of a polymer reinforced with carbon-fiber with an underlying titanium frame and comes in black, dark-green and desert-tan colors as well as the SEDENA digital camouflage patterns used by the Mexican army.The charging handle can be installed on either side of the rifle with gas piston located above the barrel, which operates under a multi-lugged rotary bolt system.Safety/fire mode selectors are located above the pistol grip on both sides of the FX-05.