Base gun is an A&K mkII m249. Upgrades were made to improve range,accuracy,reliability,and usability of the whole system. Internal Upgrades: Angel custom 500mm 6.01 TBB Umbrella armories R-hop Flat bucking SHS full metal rack piston Nukefet mosfet wired to deans Re-shimmed and re-greased Outer upgrades: Brand new outer barrel assembly Classic army metal heat shield Pressure switch for box mag FPS: 340 on a .25 RPS varies due to battery type and usage. I’M REALLY LOOKING FOR SOME SORT OF HPA CYLINDER DROP IN FOR A TRADE. I will look into offers for other LMGs and 416’s. As always cash is king and this whole deal can be yours for $225 shipped.