Floyd Mayweather -- I Know The Secret for Perky Balls

Do your balls hang low? Do they wobble to and fro? Can you tie 'em in a knot? Can you tie 'em in a bow?

If not ... and you wanna keep 'em from saggin' down to your ankles ... take a listen to Floyd Mayweather -- who says he has the secret to keep your twins high and tight for life!

Floyd revealed his secret on Showtime's "All Access -- Mayweather vs. Maidana" ... telling a few female friends why it's imperative men wear tights when they go to sleep.