Click to expand Tap to zoom Ace1Arms Polymer M4/M16 Hop-Up Chamber Unit by Ace1Arms Save Liquid error (snippets/product-badge line 32): Computation results in '-Infinity'% $17.99 SKU ACE-HOP-M4-GEN2-P 1 2 3 4 5 6 7 8 9 10+ Quantity Quantity Add to cart Features Polymer Construction Suitable for M4/M16 Series Airsoft Electric Gun AEG Rifle Enlarged, in-line adjustement dial for easy and smooth adjustment, secured by o-ring to prevent loosening.