i ordered a case from Paintballgear.com, i got the neon green as well, it is advertised as .686, altho i dont doubt that The Great Morpheus is completely wrong on his measurement, i put it in a .686 bored barrel and it fit good, but it blew out kinda easy when i tested it. i took another one and put in my .688, it rolled out. so i would use a .686 or .685 bored barrel. it worked well. altho i like all RPS advantage paint, this is great in electro's. its well worth 50 bucks and works as good as el tigre and hell fire.