The opening weekend of the 2025 MLB season was taken over by a surprise star -- torpedo bats.

The bowling pin-shaped bats became the talk of the sport after the Yankees' home run onslaught on the first Saturday of the season put it in the spotlight and the buzz hasn't slowed since.

What exactly is a torpedo bat? How does it help hitters? And how is it legal? Let's dig in.

Read: An MIT-educated professor, the Yankees and the bat that could be changing baseball

What is a torpedo bat and why is it different from a traditional MLB bat?

The idea of the torpedo bat is to take a size format -- say, 34 inches and 32 ounces -- and distribute the wood in a different geometric shape than the traditional form to ensure the fattest part of the bat is located where the player makes the most contact. Standard bats taper toward an end cap that is as thick diametrically as the sweet spot of the barrel. The torpedo bat moves some of the mass on the end of the bat about 6 to 7 inches lower, giving it a bowling-pin shape, with a much thinner end.

How does it help hitters?

The benefits for those who like swinging with it -- and not everyone who has swung it likes it -- are two-fold. Both are rooted in logic and physics. The first is that distributing more mass to the area of most frequent contact aligns with players' swing patterns and provides greater impact when bat strikes ball. Players are perpetually seeking ways to barrel more balls, and while swings that connect on the end of the bat and toward the handle probably will have worse performance than with a traditional bat, that's a tradeoff they're willing to make for the additional slug. And as hitters know, slug is what pays.

The second benefit, in theory, is increased bat speed. Imagine a sledgehammer and a broomstick that both weigh 32 ounces. The sledgehammer's weight is almost all at the end, whereas the broomstick's is distributed evenly. Which is easier to swing fast? The broomstick, of course, because shape of the sledgehammer takes more strength and effort to move. By shedding some of the weight off the end of the torpedo bat and moving it toward the middle, hitters have found it swings very similarly to a traditional model but with slightly faster bat velocity.

Why did it become such a big story so early in the 2025 MLB season?

Because the New York Yankees hit nine home runs in a game Saturday and Michael Kay, their play-by-play announcer, pointed out that some of them came from hitters using a new bat shape. The fascination was immediate. While baseball, as an industry, has implemented forward-thinking rules in recent seasons, the modification to something so fundamental and known as the shape of a bat registered as bizarre. The initial response from many who saw it: How is this legal?

OK. How is this legal?

Major League Baseball's bat regulations are relatively permissive. Currently, the rules allow for a maximum barrel diameter of 2.61 inches, a maximum length of 42 inches and a smooth and round shape. The lack of restrictions allows MLB's authorized bat manufacturers to toy with bat geometry and for the results to still fall within the regulations.

Who came up with the idea of using them?

The notion of a bowling-pin-style bat has kicked around baseball for years. Some bat manufacturers made smaller versions as training tools. But the version that's now infiltrating baseball goes back two years when a then-Yankees coach named Aaron Leanhardt started asking hitters how they should counteract the giant leaps in recent years made by pitchers.

When Yankees players responded that bigger barrels would help, Leanhardt -- an MIT-educated former Michigan physics professor who left academia to work in the sports industry -- recognized that as long as bats stayed within MLB parameters, he could change their geometry to make them a reality. Leanhardt, who left the Yankees to serve as major league field coordinator for the Miami Marlins over the winter, worked with bat manufacturers throughout the 2023 and 2024 seasons to make that a reality.

When did it first appear in MLB games?

It's unclear specifically when. But Yankees slugger Giancarlo Stanton used a torpedo bat last year and went on a home run-hitting rampage in October that helped send the Yankees to the World Series. New York Mets star Francisco Lindor also used a torpedo-style bat last year and went on to finish second in National League MVP voting.

Who are some of the other notable early users of torpedo bats?

In addition to Stanton and Lindor, Yankees hitters Anthony Volpe, Austin Wells, Jazz Chisholm Jr., Cody Bellinger and Paul Goldschmidt have used torpedoes to great success. Others who have used them in games include Tampa Bay's Junior Caminero, Minnesota's Ryan Jeffers and Toronto's Davis Schneider. And that's just the beginning. Hundreds more players are expected to test out torpedoes -- and perhaps use them in games -- in the coming weeks.

How is this different from a corked bat?

Corking bats involves drilling a hole at the end of the bat, filling it in and capping it. The use of altered bats allows players to swing faster because the material with which they replace the wood -- whether it's cork, superballs or another material -- is lighter. Any sort of bat adulteration is illegal and, if found, results in suspension.

Could a rule be changed to ban them?

Could it happen? Sure. Leagues and governing bodies have put restrictions on equipment they believe fundamentally altered fairness. Stick curvature is limited in hockey. Full-body swimsuits made of polyurethane and neoprene are banned by World Aquatics. But officials at MLB have acknowledged that the game's pendulum has swung significantly toward pitching in recent years, and if an offensive revolution comes about because of torpedo bats -- and that is far from a guarantee -- it could bring about more balance to the game. If that pendulum swings too far, MLB could alter its bat regulations, something it has done multiple times already this century.

So the torpedo bat is here to stay?

Absolutely. Bat manufacturers are cranking them out and shipping them to interested players with great urgency. Just how widely the torpedo bat is adopted is the question that will play out over the rest of the season. But it has piqued the curiosity of nearly every hitter in the big leagues, and just as pitchers toy with new pitches to see if they can marginally improve themselves, hitters will do the same with bats.

Comfort is paramount with a bat, so hitters will test them during batting practice and in cage sessions before unleashing them during the game. As time goes on, players will find specific shapes that are most comfortable to them and best suit their swing during bat-fitting sessions -- similar to how golfers seek custom clubs. But make no mistake: This is an almost-overnight alteration of the game, and "traditional or torpedo" is a question every big leaguer going forward will ask himself.