Echo1 Complete 8mm Metal Gearbox Shell for M4 / M16 Series Airsoft AEG Rifles

"I was hesitant to purchase due to how cheap the price was, however, the quality of this gearbox is great! I purchased for my Polarstar Kythera. The downside was that inside the gearbox, there are slots for gears to fit in (I assume for better stability) and significant dremeling is needed for the HPA hose to fit.

This product comes with the gearbox shell and screws ONLY. No other internals, selector plate, trigger, etc are included.

I gave this item a 4/5 due to the dremeling required for what I needed. Photos of the inside of the shell would’ve saved a lot of headache, had I known.

"I bought 2 of these and they both cracked at the front. Granted this was before I did any radius work so take it with a grain of salt but both were not high stress at all, just shooting 360 fps at around 11 rps cause I mainly used a 7.4. Not a reliable shell in my opinion.