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EMG x Retro Arms CZ Billet CNC 8mm Ver.2 Gearbox Shell for M4 / M16 Series Airsoft AEG Rifles (Color: EMG Blue)

4 Customer Reviews

by craig m. on 09/01/2021
"Worked perfect in my cm18 build. I used the prometheus 8mm bearings and they fit like a glove. I had to file one of the corners on the top on the back of the gearbox (buffer tube side) so my charge handle would fit over it when installing the upper (using a krytac aluminum upper and lower). Other then that slight modification and the tedious shimming it went together perfectly.

Parts I used for my build.

Trigger group- Jefftron Leviathan
Bearings- prometheus 8mm
Gears- matrix steel gears
Cylinder- maxx ported
Piston- hellfire
Upper and lower- krytac aluminum.
by Jordan C. on 05/15/2021
"Put this in my limited edition vfc m27 with a retro arms j trigger in the matching blue color and it's beautiful. Had my freind who owns a pro shop build it with siegetek gears and a gate titan. Yes go retro arms for a fully built aeg and a great conversation peace ✌
by Will P. on 03/02/2021
"We installed one of these for a customer, I agree with the first review, and I have to add, if somebody out there is planning to install a Gate Astor, plan to paint the inside of the box flat black. not a big deal, but its soo shiny inside that the single sided boards get all screwy with the light bouncing around. Really should use a Titan or similar, but our customer provided the parts.
by Gavin N. on 02/08/2021
"I have this in my VFC mp5, no fitment issues.

We all know how great and strong these gearboxes are so here are some things to note that aren’t as great.

- Was expecting it to come in a box, instead came in a clear plastic bag, kinda lame but didn’t affect the durability on mine
- The holes for the bushings are too small, I tried FLT, Modify, and even Retro Arms but none fit, I had to open the holes up for any to fit
- The screw used to mount the trigger contacts/board isn’t the same size as most gearboxes. Not a huge deal but why?
- The qc spring guide is nice, but the torx head on the back is wayyyy too big, retro arms even sell a screw-in knob for the guide. Again, why?