The Prophet II has a new assisted valve, a new breech block with an integrated 70ccm plenum, and new RPB barrels in 5,5mm (.22) and 6,35 (.25) which shoot slugs as well as pellets very well. The new valve is much more efficient and allows for greater power with lower pressure settings than with the original Prophet. You will also notice other minor features such as the cocking handle staying fixed in its forward position, unlike with the original Prophet with which it was rather loose.