Barrel covers are required at a lot of airsoft venues. They are useful for protecting other players in staging areas from accidental discharges from your airsoft guns. It is important to have a barrel cover for all of your guns and why not represent Building 52?
These barrel covers are wide enough to fit over most airsoft gun muzzles.
Building 52 recommends writing your name or other identifying information on your barrel cover. This is in case it gets lost or mixed up with someone else's. You can use a magic marker on the red area to write your name.