The Freak Junior Barrel Kit by GoG Paintball is one of the best ways to improve your shooting accuracy, in any weather, at any time. This is a two piece barrel, but features an innovative insert system. The inserts are sized to specific bore sizes, and slide into the barrel back. When you fire a paintball and it passes through the barrel, it will first come into contact with the insert, if properly sized, the insert will put the paintball on a straight trajectory. The Junior barrel kit comes with three inserts, they are sized .687, .689, and .691. They also sell individual inserts so you can create your ultimate barrel kit. Another huge advantage to these barrel kits is their flexibility.. Say in a few months you change from one paintball marker type to a different one with different barrel threads. Instead of having to buy a complete new kit, you can just buy the appropriate barrel back.