It's not what you think. In fact, if you guessed "they're famous for no reason," obviously you haven't seen our boy Zac in High School Musical. Just saying.
Nicole Richie, Zac Efron are among several young stars recently spotted rocking crimson bracelets - much like the red Kabbalah string Madonna made famous a few years ago.
Is the trend making a comeback?
Richie (pictured here with the string on her limp, bony arm) and Lauren Conrad - also spotted wearing the string of late - each have been sporting a charm of a hand on them called a "hamsa," explains Rabbi Shmuley Boteach of TLC's Shalom in the Home.
"It's a kabbalistic symbol. Wearing it is meant to bring down God's mercy and kindness."
But a rep for Zac Efron (who's girlfriend, Vanessa Hudgens, also wears one), tells Us Weekly that his bracelet has no significance.
"It's not a kabbalah string," the rep said.
"There's no religious meaning [to the red string]."
Meanwhile, Lauren Conrad's rivals on The Hills, Heidi Montag and Spencer Pratt, are probably rushing to try and patent string, as well as the color red, so they can cash in on this fad.