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  • Version 2 Compatible
  • Precion CNC Machined
  • For Custom Gearbox Builds

    Designed to allow Airsofters to build their own custom Version.2 Gearbox for their Airsoft Electric Gun. 

    • Rotary HOP-Up Adjuster
    • CNC Aluminium Construction
    • Includes flat & conventional HOP arms

    If you're building your M4/AR-15 AEG to focus on range, accuracy and efficiency, the RetroArms CNC Rotary HOP-Up Chamber Gen.2 for M4/AR-15 AEG belongs in your build. This set is a full replacement rotary type HOP-Up unit for version 2 gearbox-equipped Airsoft M4/AR-15 platform AEGs and includes all of the parts you'll need to replace your stock HOP-up unit. The set also includes the choice of two HOP-up arms, one designed for flat HOP setups and one for conventional.

    As with all internal upgrade parts, we only recommend this HOP-up unit for the technically proficient as it requires full assembly and does not include a HOP-up rubber or HOP-up nub. That said, the RetroArms CNC Rotary HOP-Up Chamber Gen.2 for M4/AR-15 AEG is widely regarded as one of the best options out there for the pros, and when set up properly, it has the potential to outrange anything else on site!

    About RetroArms

    RetroArms specialise in Airsoft parts and upgrades, so if you're looking to augment your replica, RetroArms are a great choice. Their key Airsoft-specific items are CNC machined flat triggers to upgrade your gun to a speedy shooting machine. 

    Also in RetroArms repertoire are their lines of machine screws, used for pistol heads, gearboxes and more.