Shipping is free, included in price. Gun: APS ASR115X M4 Internals: Matrix CNC steel pinion gear Matrix CNC Aluminum double O-ring piston head Maple leaf 80 degree rubber bucking Maxx ME-PRO Hopup Chamber ZCI steel 16:1 gear set Prometheus M135 spring Matrix 37,500 rpm balance torque/speed motor Barrel is stock because it was good, but Rubber Bucking, and hopup chamber are set for flat hop. Radiused gear box cleaned, re-greased, and oiled everything Set AOE properly tighten everything down