King Arms M4 Metal Hop-Up Chamber for AEG google the exterior features PALS webbing

the exterior features PALS webbing on the sides and shock cord on the backside to stow an outer garment for easy accessibility

Modification may need for installing this kit on the other brand M4 GBB Series

Able to increase the muzzle velocity)

Featuring an extremely long inner barrel and a super high capacity cylinder

Include 8mm Ball Bearing

King Arms M4 Metal Hop-Up Chamber for AEG google the exterior features PALS webbingThis One Piece Metal Chamber Set is more durable and accurate in feeding BB Improves Firmness of the chamber & stabilizes the muzzle velocity O Ring Sealed Design to Improve Air Seal Re Designed Hop Up System prevent loosening New Barrel Lock shape for holding barrel more securely Unlike stock plastic chamber which would bend & de shape, this metal one give you rigidity Highly recommend for upgraded Airsoft Electric Gun to withstand higher air