For the original Prophet, the differences are that the Performance version comes with an externally adjustable regulator, a 500cc carbon fiber bottle, an extended stock with adjustable hammer spring tension, and plenum extension, while the standard version has a fixed regulator, a 320cc aluminum bottle, standard stock, and no plenum extension. With the Prophet II, the differences are mainly the externally adjustable regulator, the adjustable hammer spring tension, and the larger carbon fiber bottle. The plenum is already much larger than with the original Prophet, hence no plenum extension is needed.