Polarstar JACK - HPA Standard FCU Conversion Kit Spring Shotguns Uses UMP magazines - hicap

Uses UMP magazines - hicap or midcap

Sniper grade airsoft BBs for its very heavy weight

steel gears

Here are a few highlights

2021 update:  Will fit the Valken 11

Polarstar JACK - HPA Standard FCU Conversion Kit Spring Shotguns Uses UMP magazines - hicapThe 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)