RetroArms CNC Hop-up Unit M4 / AR15 PRO − Black

CNC Hop-Up Unit AR15 PRO by RetroArms

The AR15 PRO hop-up unit by Czech manufacturer RetroArms is a premium choice for AEG replicas based on the AR15/M4 platform. Based on the proven BASIC version, the PRO model adds several key upgrades for enhanced reliability and magazine compatibility. The unit body is precision CNC-machined from EN AW 7075 aircraft-grade aluminum. A standout feature is the adjustable magazine well height in 0.2 mm increments using stainless steel shims, helping to resolve feeding issues caused by poor magazine seating. After setting the correct height, it's recommended to secure the threads with a drop of thread locker. The unit inlet includes an O-ring to prevent BBs from falling out during reloads. A collet-style barrel nut ensures automatic barrel centering and eliminates movement during firing – compatible with inner barrels of 8.4–8.5 mm outer diameter. The PRO version features enhanced internal tolerances for improved BB feeding and is fully compatible with most hop-up buckings.

Comparison of BASIC, PRO, and ULTRA Hop-Up Unit Models

1. BASIC
   The ideal option for players seeking a reliable and accurate unit without extra tuning. Made from EN AW 7075 aluminum, includes an O-ring inlet and collet nut for barrel centering. Ready for R-hop and compatible with most buckings and inner barrels. Offers a great price-performance ratio and easy installation.
   
   
2. PRO
   Based on the BASIC version, the PRO adds an adjustable magazine well height in 0.2 mm steps for better magazine compatibility with certain AR15 builds. It retains the collet nut, O-ring inlet, and CNC construction. Ideal for users who want reliability and fine-tuned feeding.
   
   
3. ULTRA
   Designed for advanced players who want a fully customizable unit. Adds adjustable longitudinal positioning relative to the gearbox, along with an upgraded POM lock and clamping nut system that eliminates any barrel shift. Also features a flat, extended bucking channel compatible with ROBUST no-lip hop-up buckings. The ULTRA is RetroArms' most advanced model, built for complete fine-tuning.

Key Features

• High-strength EN AW 7075 construction
  Maximum durability and precision with CNC machining.
  
  
• Adjustable magazine well height
  Perfect magazine fit using 0.2 mm shim adjustments.
  
  
• Collet nut for barrel centering
  Prevents barrel shift and improves shot consistency.
  
  
• O-ring unit inlet
  Prevents BBs from falling out when reloading.
  
  
• Enhanced compatibility
  Supports most hop-up buckings and 8.4–8.5 mm inner barrels.

Technical Specifications

• Material: Aircraft-grade EN AW 7075 aluminum (CNC machined)
• Unit type: AEG for AR15/M4
• Unit inlet: With O-ring
• Barrel locking: Collet nut (for 8.4–8.5 mm barrels)
• Magazine well height adjustment: 0–1 mm in 0.2 mm increments (with stainless shims)
• Compatibility: Tokyo Marui AEG standard (most hop-up buckings)

Package Contents

• CNC Hop-Up Unit AR15 PRO
• Collet nut
• Stainless shim set for height adjustment