Polarstar JACK - HPA Standard FCU Conversion Kit Version:V2 M249 (1) Enhanced mode

(1) Enhanced mode

If you're unsure of what gun to purchase

realistic blow back action

May fit in some odd guns too

rear stock and twist the buttplate in either direction (see picture)

Polarstar JACK - HPA Standard FCU Conversion Kit Version:V2 M249 (1) Enhanced modeThe Polarstar JACK HPA Standard FCU Conversion Kit. This is the full sized FCU version for easy programming. Contains everything you need internally. Works drop in with most M4 AK platforms. G&G, Elite Force, JG, and most are pretty easy to install. Watch some Youtube videos on how to put it in yourself. With the Polarstar JACK engine, all you need to complete your HPA setup is: HPA Air Tank (non SLP tan regulator is okay, Ninja, Valken, FS is good)