For his upcoming fight against Filipino boxer Manny Pacquiao on May 2 at the MGM Grand Arena in Las Vegas, undefeated American fighter Floyd Mayweather Jr. will be wearing a $25,000-smile with a mouthpiece stuffed with $100 bills.

The expensive mouthpiece, according to the New York Daily News, came from Iceberg Guards of New York and Dr. Lee Gause who has reportedly been working with Mayweather for his last five fights.

"Athletes don't like mouthguards because they can't breathe with them. If you watch the [Miguel] Cotto fight, you'll see he pops his mouthguard out about 15 times. Then you see Floyd, and he drinks water with it in, talks to his trainer in the corner. He never pops it out during the compeition," Gause explained to New York Daily News.

The doctor added that perfecting the mouthguard was a long process especially that Mayweather is a "perfectionist." Gause refused to reveal the secret on how they made the mouthpiece but noted that it was designed to help the boxer breathe better.

"The claim that we're making is that these will make you breathe better. Our mouthguard may be one percent better than the competition, but one percent is the difference between winning and losing. Good athletes and great atheltes are in tune with that one percent," the doctor added.

He also noted that the American fighter also wants to be protected from potential dangers of concussions so he asked for a mouthguard that would really protect him from that despite its high price tag.

A similar TMZ Sports article noted that the mouthpiece he will be wearing for the megafight is stuffed with real $100 bills.

The same report added that this has been a common practice for Mayweather as he likes to "customize his guards with things like gold flakes, diamonds and real $100 bills (sealed inside the mouthguard) ... ups the price from the regular pieces."

In an interview with TMZ, the boxer said that despite his long years of boxing, he still has a great smile.

"My career's gone on 19 years and I've been able to preserve my smile," Mayweather added.

Surely, Mayweather can afford those pricey mouthguards as he was declared the highest earning athlete in 2014 by Forbes.

His fight against Pacquiao will be aired by both Showtime and HBO which has already released the first commercial of the fight. Daily Mail said the marketing team of the two camps came up with a 30-second clip which was shot in an LA studio last March 11. The official advert showed Pacman and "The Money" walking towards each other in the middle of a desert with the MGM Grand Arena as their background.

"It's time. Two legends. One destiny. All roads end here," said the commentary which prepares expectations of the audience for one of the richest fights in boxing history.