its a weight
some players like swinging with extra weight to quicken their swing and loosen up
"I swear, if something bad happens to my friends, I'll rip every tooth out of that shark and make it into the most beautiful necklace you've ever seen."
donny x2
or u can do the 3 bat drill.
its so u can get better bat speed cuz in mlb when guys throwing 90 u cant catch up without some sort of weight before it.