Click to expand Tap to zoom Ace1Arms CNC M4/M16 Rotary Hop-Up Chamber Unit by Ace1Arms Save Liquid error (snippets/product-badge line 32): Computation results in '-Infinity'% $39.99 SKU ACE-HOP-M4-GEN2 1 2 3 4 5 6 7 8 9 10+ Quantity Quantity Add to cart Features CNC Aluminum Construction Design to replace the original Hop-up chamber Suitable for most M4/M16 AEG