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Retro Arms CNC Machined Aluminum Rotary Hop-Up Unit for M4 Series Airsoft AEGs - Red

ID: 59004 (HU-Retro-6388)
Retro Arms59004
4.1 stars, based on 8 reviews
Retro Arms CNC Machined Aluminum Rotary Hop-Up Unit for M4 Series Airsoft AEGs - Red
Hover or touch above to zoom
May come in black or silver anodized coating, depending on batch



  • CNC machined construction
  • Rotary design allows for easy adjustment
  • Constructed from EN AW 7075 for extended lifespan
  • All necessary hardware included
  • Bucking not included
Compatibility: Most M4 series Airsoft AEGs
Material: Aluminum alloy

Manufacturer: Retro Arms

California residents click here for Proposition 65 warning

8 Customer Reviews

(Write a review)

by Nash G. on 05/09/2018
"As a Tech for my team using KWA and Ares rifles, I've heard a lot of back and fourth from team members about which is better. Personally, I've found it depends on the build. For quick adjustments, a pro-win is the obvious answer (Please Look at my review on the Pro-Win for details.). The Retro arms dial is very stiff but this benefits long range, tuned builds. My personal build, an Ares M110, (one of these tuned builds) uses the benefit of stiffness as it has never lost pressure on the nub in an engagement at 200+ feet (100 meter shoots are possible with this hop up with .4bbs and a Tight bore of your choice), something important when you are counter snipping. I would recommend Flat hopping on both builds if you want to get the best performance. (Unless you can R-hop) Either is a good choice. But After my previous issues with the pro-win (late 2017), I will be sticking with retro-arms until they increase QC.

--Retro Arms-- (Good for long range builds)
Stiff and doesnt move once you set it.
2 ways to tension the barrel,
large window for the nub
Doesn't Fit stock KWAs (Vers 2.5+), Some G&P, or most Ares without cutting

--Pro-Win-- (Good for the everyday user, and with a little work, long range builds)
Fits most TM style guns
Easy to adjust for quick games
Large window for nub (slightly smaller than retro arms)
Doesnt fit Stock KWA (Vers 2.5+) or Ares (M110, cant speak for others)

Red Devil Works Tech
by Severino C. on 02/20/2018
"The hop dial does not turn smoothly, very difficult to adjust once it is already installed in the receiver. Better off buying prowin or something similar in design...heck your stock hop is better than this one.
by Austin L. on 02/12/2018
"Stupidly good hopup, like other reviews said you will have to trim your bucking but that does not affect performance in the slightest. The grooves inside the turn wheel make it a super solid turn that won't wiggle out of place during use. Also once you screw in the nut for the inner barrel it makes it tight with no wiggle at all. The only thing I had to do was shave my outer barrel a bit to make it fit inside the receiver, but that took two minutes with a file and it was perfect. Beware like other rotary hopups it stands high so it might be to tall for your receiver. All in all it reminds me a lot of the action army hopup for vsr10's in how it operates and once I get this thing out to areas bigger than my local cqb place I'm expecting easy 275ft+ shots on a r-hopped barrel/polarstar setup. 5/5

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