Louisville Slugger XX Prime Birch Wood. 33.5 inches not cupped. For over 125 years, Louisville Slugger wood bats have been in the hands of some of the game's biggest stars. Still to this day, more teams and players swing Louisville Slugger than any other brand.  The ball players XX Prime Birch model features MLB Prime grade Birch wood with a slight defect, a pro cupped end and a large barrel. The XX Prime bats are X-Out models of the same MLB Prime bats the pros are swinging. Birch is lighter in weight than maple so you can still have a large barrel bat with strong wood without sacrificing on quality. If you want to get the most out of your game this season, swing what the pros swing.