Some players perform better with a stiff handle bat. Until now those players had to compromise a sweet feeling bat for peak performance because as a bat gets stiffer, its vibrational response increases. By incorporating Ph. D technology (Passive Hybrid Damping) into stiff handle bat designs, the need for compromise is over. Ph. D is the ultimate in vibration reduction technology, it will revolutionize the feel of stiff handle bats because it filters out harsh vibration more effectively than any previous technologies.