Polarstar JACK - HPA Standard FCU Conversion Kit Military & Government Airsoft Training Guns Also have integrated backup sights

Also have integrated backup sights on top

All other settings are internally regulated

It has two zippers on top

The model 19 is a little smaller in size than the 17

Only use the cylinder head this kit comes with

Polarstar JACK - HPA Standard FCU Conversion Kit Military & Government Airsoft Training Guns Also have integrated backup sightsThe 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)