There is really no such thing as MBUS 2. It's actually just a second generation "MBUS", or MBUS Gen 2. The Gen 1 is being discontinued and replaced by the Gen 2 just like we did with PRS and the Enhanced Self-Leveling Follower (now on Gen 3 actually). The number two as in PRS2 or AFG2 means that it is a different product with the original still in production. I guess the only exception to this would be the MS2 Sling as the two was just part of its name.