Now available at Laylax is the FFactory TM M4A1 MWS GBB Barrel Spacer. If you intend to attach another rail handguard to replace the existing one and is more designed for a Marui-compatible M4A1 AEG, then you will have problems of not having a good fit. This outer barrel spacer was designed to fix that problem.
Modify-Tech have released their Barrel Spacer for their MOD24 Sniper Rifle due to customer demand... "The MOD24 barrel spacers have recently been the most frequently inquired, now we are going to release the barrel spacer for MOD24. The outside double O-rings to keep best position. We also add an O-ring inside each to stabilize the inner barrel and reduce vibration. The barrel spacer is made of POM. It is light and solid with the best material."