I bought the base kit then later bought the 12 inch and then 14 inch tip for my autococker and switch it back and forth on my sniper II. I gotta tell you, it's a good barrell system. It quiets your shots and is accurate. And the obvious benefit is the ability to switch bore sizes and tip lengths. It also comes in a variety of colors for the tips.
The bore section of the barrel scratches pretty easy. It also doesn't come with barrel o-rings which are defintely a must.