Throughout baseball diamonds across the country, teams are getting back into the swing of the season. Like their big-league counterparts, Little League and recreational players will sport leather gloves, cleats, and umpire’s gear.

But there’s one piece of equipment some players will opt for that won’t be seen in any Major League Baseball (MLB) game—an aluminum bat. It’s the difference between the crack of a wooden stick and the ping or bink of a baseball colliding with aluminum.

The reason? Pro players are just too good.

Both the major and minor leagues have banned the metal bat because of the skill level of their participants. Thanks to the “trampoline effect,” a metal bat will have a slight give when connecting with the ball, transferring more energy. It becomes easier for hits to travel farther and faster, with their velocity known as bat-exit speed. Some players have even been known to break in a new aluminum bat to allow for greater flex in the material by running over it with a car.

When aluminum bats were first introduced in the 1970s, NCAA teams saw batting averages go up 20 points; home runs doubled. If aluminum and other metal bats were allowed, observers believe the technology would supersede player talent. Records would be shattered, and the game might be diminished.

“We once had a couple aluminum bats around the big-league batting cage,” Cal Ripken Jr. told The Baltimore Sun in 2018. “I remember [fellow Baltimore Orioles player and second baseman] Robbie Alomar picked one up in Oakland, and he was going so far into the bleachers to straightaway center that it was almost ridiculous.”

Little Leaguers and rec leagues don’t typically see that kind of power. In fact, an aluminum bat can make learning the game easier. Wood bats tend to have their weight in the barrel, and connecting without splintering usually means hitting the ball near the label; metal bats are more forgiving when it comes to ball placement. Because they’re hollow, they’re also lighter, making them easier for small hands to grip and swing. (A bat’s weight depends on its length, but generally, aluminum bats are around 5 ounces lighter.)

Because aluminum bats are speeding up the ball, there is potential for injury, although it’s relatively rare. Still, the New York City Council banned metal bats in high school games in 2008. New Mexico also prohibits them. In 2018, USA Baseball, which supervises youth organizations like Little League, mandated a new type of bat that’s aluminum but performs more like wood.

[h/t The Baltimore Sun]