Cybergun SIG 550 AEG The Sig 550 rifle by Cybergun is a great reproduction and licensed copy of the Swiss Arms Sig 550 assault rifle. The long 20.8 inch barrel and comfortable stock makes this rifle perfect for use as a Designated Marksman Rifle in medium to long distance engagements. The upper receiver, lower receiver, bi-pod, and barrel assembly are an aluminum alloy. The rest of the parts are a durable blend of nylon, fiberglass, and plastic able to withstand all but the most vicious of abuse. The gun comes with a 300 round high capacity magazine but replacements are readily available. As if it couldn't get better, this rifle comes standard with a built in metal bi-pod for increased accuracy in support and sniper roles and a built in rail for easy optic attachment. The battery compartment is ingeniously designed and located inside the forearm of the rifle and can be difficult the first time to install. First push down and twist the gas adjust valve and remove. The top handguard half can then be pushed down and removed exposing the battery sheath. Reverse the process and you're good to go. Airsoft players recommend using this rifle in a Designated Marksman or sniper role for best results. Do not use .12g BBs with this gun!