Nineball 6.00 inner Power Barrel - 5" (112.5mm)
One of the best barrels you can get.
Nice bump in FPS as well as an increase in consistency and accuracy.
Make sure when you're using one of these you use high quality BBs.
compatible with the 5.1 and 4.3 capas, they do work brilliantly with a 4.3 outer barrel and a thread adapter.