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We all know the rumor about men and big feet. But what if we told you the truth was really in his fingers? Men with ring fingers longer than their index finger on their right hand (yes, we are being that specific) have larger testicles, according to a study from Department of Urology at Gachon University Gil Hospital in South Korea.

Doctors took finger measurements from 172 men ages 20 to 69. And while the link between testicles and finger length may seem random, it's not. The study was carried out because of a hunch that the index to ring finger ratio correlated with the male reproductive system. Previous research on Hox genes-genes that control finger development and genital development in embryos, and act like a map for how the body will look when it is fully formed-suggests the connection.

But does this trick really work? "Higher testosterone levels during fetal development have shown to have a correlation to the size of a man's ring finger compared to his index finger," says Emily Morse, sexologist, and host of the Sex With Emily podcast. "I'm not suggesting anyone rule out any potential mates based on their hand print, but I can say that testosterone and the ratio between the index finger and ring finger could have some potentially useful data."

But does testicle size matter? Various studies suggest that the size of a man's testicle is related to the volume of semen he is able to produce. (That means increased fertility.) But let's be real, no one is breaking out a ruler on the first date-and testicle size isn't the most pressing sexual information you're going to want to know about a potential love interest. That said, want to know how he stacks up compared to other guys when it comes to penis size, porn, previous partners, protection (and more!) without being so-ahem-obvious? We compiled the data for you here.