Polarstar JACK - HPA Standard FCU Conversion Kit Multicam The barrel end is 6

The barrel end is 6

This is for the mount system only

Fire modes include semi and full auto

but not for the Action Army Hop up Chamber

but is a very tight fit with the A5 handguard

Polarstar JACK - HPA Standard FCU Conversion Kit Multicam The barrel end is 6The 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)