Floyd Mayweather Jr.'s nickname these days is "Money," but earlier in his career he went by "Pretty Boy" Floyd. As a master of in-ring defense, Mayweather can go by either moniker these days. He has seldom seen the sight of his own blood, and regularly goes 12 rounds unscathed. Some of the credit for that might go to his exceptionally expensive mouthpieces.

Mayweather gets his mouthpieces custom made by renowned dentist Dr. Lee Gause, and often has gaudy items placed inside them. These mouthpieces go for around $25,000 each-against Manny Pacquiao on May 2, Mayweather will have $100 bills inside his mouth guard.

Really.

Want to see the mouthpiece? Here it is

"My career's gone on 19 years and I've been able to preserve my smile," Mayweather told TMZ. These mouthpieces serve more than just his taste for the lavish though. Mayweather also told TMZ that the custom mouth guards help him breathe better inside the ring. As a defensive-minded fighter who hasn't knocked out an opponent since 2011, stamina is crucial to maintaining his perfect record.

Many expect the mouthpiece's effectiveness to be tested in this fight. Not long ago Pacquiao was considered at least an equal to Mayweather atop the mythical pound-for-pound rankings, and is still a much closer underdog than most of Mayweather's foes. Vegasinsider.com has Pacquiao listed at +170 to upset Mayweather.

As a comparison, in Mayweather's September 2014 fight against Marcos "El Chino" Maidana, "Money" was -800, and the challenger was +500. Those odds were installed after Maidana had given Mayweather one of his stiffest challenges of his career and bloodied him.