Smart Parts' major barrel product is the Freak barrel system. This is an "insert" barrel kit, where the user selects one of a number of different-sized bore inserts to use (eight different sizes and a barrel back and barrel tip come with the full Freak kit). There is a total of 9 inserts in normal sizes and a 10th one (reball sized). The boremaster sets are: the aluminum boremaster set is .679.682.684.687.689.691.693,and .695 and the stainless boremaster set is .682.684.687.689.691.693.695,and .697. The insert is then installed in the back of the barrel (a two-piece barrel plus the insert, making three pieces total). The alternative to this is a "multi-bore" kit that consists of varied barrel backs for a two-piece barrel. The advantages to using an insert instead of a multi-back kit is greatly reduced price and versatility of use on more than one type of marker. The disadvantage is that inserts are more fragile (aluminium more so than the stainless) than a typical barrel back, so care must be taken.