<Li> The bat may consist of any safe solid uniform material; the National Federation of State High School Associations rules state only "wood or non-wood" material . </Li> <Li> To be legally used in a game, an aluminum bat has to be a BBCOR (Batted Ball Coefficient of Restitution) bat because it has been determined that a pitcher loses the ability to protect himself when this ratio is exceeded . </Li> <P> In some 12 - year - old - and - under youth leagues (such as Little League baseball), the bat may not be more than 2 ⁄ inches (57 mm) in diameter . However, in many other leagues (like PONY League Baseball, and Cal Ripken League Baseball), the bat may not be more than 2 ⁄ inches (70 mm) in diameter . </P> <P> There are limitations to how much and where a baseball player may apply pine tar to a baseball bat . According to Rule 1.10 (c) of the Major League Baseball Rulebook, it is not allowed more than 18 inches up from the bottom handle . An infamous example of the rule in execution is the Pine Tar Incident on July 24, 1983 . Rules 1.10 and 6.06 were later changed to reflect the intent of Major League Baseball, as exemplified by the league president's ruling . Rule 1.10 now only requires that the bat be removed from the game if discovered after being used in a game; it no longer necessitates any change to the results of any play which may have taken place . Rule 6.06 refers only to bats that are "altered or tampered with in such a way to improve the distance factor or cause an unusual reaction on the baseball . This includes, bats that are filled, flat - surfaced, nailed, hollowed, grooved or covered with a substance such as paraffin, wax, etc ." It no longer makes any mention of an "illegally batted ball". In 2001, MLB approved the use of Gorilla Gold Grip Enhancer in major and minor league games as an alternative to pine tar . </P>

What kind of bat is used in mlb