After reading several articles regarding studies showing that adding weight (donut, sleeve, etc.) to the barrel of a bat not only decreases the hitters bat speed once the weight is removed, it also creates "casting" in the swing - there was only one solution: adding weight to the knob of the bat rather than the barrel; thus the Hitting KnobTM.
By adding weight to the knob it trains the batter to swing the knob of the bat not the barrel, keeping the hitters hands inside the baseball/softball. This allows the barrel of the bat to get on a parallel path early on and stay in the zone throughout the swing; creating a whip-like motion with the barrel.
Having the weight on the knob of the bat ultimately increases bat speed and power once the weight is removed. Take a look at the SCIENCE to learn more.
Check out this article on weighting the barrel of the bat.