The Original Iron Gloves Thermal Bat Warmer Is Simply The Best Bat Warmer in Baseball and Softball. They are legal and approved to be used during play. They keep your bat 40% warmer than the outside temperature. Helps prevent dings and improves bat performance. Reduces damage in colder weather. Includes ID tag for quick identification. Patented design hangs bat easily from the fence. #1 Bat Cover in America. Fits all 2 5/8" and 2 3/4" Big Barrel Bats.