Louisville Slugger MLB Prime wood bats feature the ink dot. The ink dot is the stamp of the highest quality wood bat. Louisville Slugger ink-dotted bats that meet slope of grain are approved for play in Major League Baseball. Every maple and birch Louisville Prime bat carries this stamp of approval. Powerized which represents the highest quality care and craftsmanship that can be put into the making of a Louisville Slugger wood bat. Only MLB Prime bats will carry the Powerized mark. The current Prime bats now feature Exo Armor, a revolutionary finish that doubles the surface hardness from previous Prime bats; making the new line of Prime the hardest bats in the game. Engineered for maximum hardness, this finish is sprayed on each bat with a least 3 layers to ensure superior feel and unmatched sound upon contact.