This is a custom M4 I built from the ground up Completely custom list of all the parts below :retro arms gearbox shell :polarstar kythera engine *semi only* :maxx model hop up with a flat hopped prom purple :Prometheus R hopped barrel :maxx model adjustable trigger :uvt 106 tracer unit :G & G SSG1 drop stock :PTS Griffin Armament hand guard 8.6 :EMG F1 receiver :Alien Armory grip