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

ID: 90801 (HU-Retro-7221)
Retro Arms859188908017722190801
3.0 stars, based on 1 reviews
Retro Arms CNC Machined Aluminum Rotary Hop-Up Unit for ICS M4 Series Airsoft AEGs
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Retro Arms



  • CNC machined construction
  • Rotary design allows for easy adjustment
  • Constructed from EN AW 7075 for extended lifespan
  • All necessary hardware included
  • Bucking not included

Manufacturer: Retro Arms


Compatibility: ICS M4 Series Airsoft AEGs
Material: Aluminum Alloy

1 Customer Review

(Write a review)

by Minh P. on 02/02/2020
"I purchased this hop up unit since it is compatible with ICS M4 AEGs. I was stoked that Retro Arms is now making after market parts for ICS because they have been known to create superb gearbox products. I was really hoping that is would be a better alternative than the stock hop up unit or the MAXX MI hop up unit (since it's cheaper).

When I first received this product, it was tightly packed in a small clear plastic ziploc bag. The hop up unit itself had a weird oily texture in my hands, and dry yellow-ish strains like from the advertising picture. The hop up unit comes with everything it needs, however, I was surprised that the hop up unit also came with a R-hop tensioner that is quite similar to MAXX hop up units (Evike didn't state that in the description or had pictures of it). The built quality of the hop up unit has a rough finish that isn't as smooth as the older Prowin hop up units. No instructions came with the hop up unit, so if you're familiar with rotary style hop up units, assembling it is intuitive.

Now, I have ONLY one major complaint and gripe about this product. The tolerance of this hop up unit is so tight that adjusting the rotary dial for hop up is nearly IMPOSSIBLE to do. The amount of effort to just turn a millimeter is ridiculous. Never ever in my whole 10+ years of airsoft experience have I seen an airsoft hop up unit function like this. I am not sure that with use and over time the rotary dial will break in and be more loose.

I am currently using the hop up unit in my ICS MMR SBR AEG, paired with a Prometheus 6.03 285mm inner barrel with the Modify Ryusoku flat bucking. I have noticed a 7 - 10 fps increase, that isn't as consistence unlike the stock hop up unit. The hop up unit is able to feed from my KWA K120 midcap magazines (there is 2 - 3mm of wobble). I haven't had the chance to test the hop up unit accuracy or range, but I plan on sharing my experience once I do.

Would I recommend this product for ICS M4 owners? Probably not. Stick with the metal stock hop up unit.

FPS increase 7 - 10
Rotary style
Fits in ICS M4 AEGs
Comes with R-hop tensioner

Rotary dial impossible to adjust for hop up
FPS inconsistency
Rough finish

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