Umbrella Armory x Maxx Model Precision Hop-up Unit (M4A)

Type: Part
Maxx Model M4A pro hop-up unit, M4/V2 AEG type. Featuring R-Hop specific adjustment wheel for greater flexibility and ease with tuning hop amount.

This hopup improves on the Maxxpro ME design by increasing the flat traveling nub's surface area with the hopup. Minimizing uneven pressure, and tilting of the nub.

We recommend using O-rings to space the hopup unit. Our unit doesn't include the top spring, or extra nubs as they are not utilized.

You can use the 6mm nub for small or large windowed hopup units.

We strongly recommend double checking your air nozzle clearance with the M4A hopup unit. Many users who utilize 21.3mm nozzles, may have feeding issues. In our testing, most air nozzles between 20.8mm-21.00mm have much better success at high ROF feeding.

If our printed spacers are used. The side wings are fitted for VFC and Krytac outerbarrels, but work very well with most other outer barrels. If installed, you may need to sand the wings slightly down as its intended to be a snug fit to mate the hopup dead center to the outerbarrel. This may result in needing to shim the gearbox to be centered. Expert install is recommended.
The bottom magazine feeding spacer was intended as nearly all VFCs we've encountered seem to have issues with specifically EPM1 magazines, and sometimes will improve EPM magazines. You should only use this spacer if your magazine is clearly loose in your gun, and if "holding" the magazine upwards helps you with feeding.


  • Dimension: 51x37.75x23 millimeter
  • Weight: 14 gram
  • Type: M4 rotary
  • For compatible V2 AEG/HPA
  • Intended for use with R-Hopped barrels
  • Numbered adjustment wheel
  • BB retention latch
  • Side windows
  • Compatible with Maxx Model hop up tracer device (not included)
  • Delrin c-clip and pictured springs included
  • 6mm (Installed) Soft Nub


  • CNC Aluminum 6061 hop-up chamber and arm
  • Delrin c-clip


  • Compatibility may vary
  • Non-Retail Packaging
  • 3D Printed Resin Spacers Sold Separately. Click Here
  • Return policy


Customer Reviews

Based on 1 review
Alex Krizanek

Love this thing, looks awesome, performs awesome, it’s awesome.