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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)

ID: 18709 (GB-EMGxRA-CNCV2-BU)
6392 CNC Gearbox Ver. II 8mm - EMG - BLUE
EMG8591881870926392 CNC Gearbox Ver. II 8mm - EMG - BLUE18709
4.5 stars, based on 4 reviews
EMG x Retro Arms CZ Billet CNC 8mm Ver.2 Gearbox Shell for M4 / M16 Series Airsoft AEG Rifles (Color: EMG Blue)
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EMGRetro ArmsEvike Exclusive


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Color Options:


  • Precision machined from a block of billet EN AW 7075 T651 aluminum
  • Quick change spring guide system
  • Durable anodized finish
  • Reinforcement in key stress points to counter rapid wear from high performance parts
  • Pre-radiused cylinder windows - helps evenly distribute impact force
  • Deeper wire channels along base of gearbox
  • EMG Logo engraved on side of gearbox
Unlike most other gearbox shells on the market, the Retro Arms CZ gearbox shells are precision CNC machined out of a solid block of billet EN AW 7075 T651 aluminum giving them unmatched durability and resilience. Combined with reinforcement of key stress points and stainless steel connecting bolts, the gearbox shell has undergone extensive stress tests with M160 springs without any signs of wear.

Version 2 Retro Arms gearboxes feature a quick-change ball-bearing spring guide mechanism, allowing spring swaps in a matter of minutes without complete gearbox disassembly.

Manufacturer: EMG x Retro Arms CZ

Color: EMG Blue


Compatibility: For Tokyo Marui, G&P, Matrix and other compatible M4 / M16 Series Airsoft AEG Rifles (Modification may be required depending on brand and model)
Material: CNC Billet EN AW 7075 T651 Aluminum

Disclaimer: Please use discretion when installing custom parts as fit and compatibility may vary. Some modification may be required. Professional installation recommended.

About EMG

The EMG vision is to manufacture products the world has never seen before; products we would put our name on, and products that hit the spot! "EMG" (Evike Manufacturing Group) was spawned from the realization that if you want something done exactly the way you want it, you need to do it yourself, and we did just that.
We took our 16 years of knowledge as the market's lead retailer, our network of 300+ superior manufacturers, to work with inspiring top innovators in the firearms industry. That combined with the vision to invest into the Airsoft industry, an industry we believe in, EMG was born.

About Evike Exclusive

At, we believe that superior outdoor recreational products can create a better world. That is why we develop, innovate, and pioneer to bring you the perfect experience, service, and products.

4 Customer Reviews

(Write a review)

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.

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