A giant knob you can stick on the back of your phone is taking off with celebrities — and it's on track to sell 30 million this year

The PopSocket, an expanding stand and phone grip, has skyrocketed in popularity and has become a top-selling smartphone accessory.
The company plans to sell as many as 30 million PopSockets in 2017, and has plans to ramp up its international market next year.

Over the past year, you may have noticed more and more smartphones sporting one increasingly ubiquitous accessory: a colorful, rubbery knob attached smack dab in the center of their backs.

Turns out, the knob has a name. It's called a PopSocket, and for the past year, it's been taking the smartphone accessory market by storm, with the trend even catching on with celebrities.

Barnett says he has ambitious plans for the company's future and that the PopSocket is only the beginning. PopSockets LLC, which has production facilities in China, Korea, Mexico, and Seattle, will roll out a set of car vent mounts and PopSockets that double as wallet holders over the course of the next few months, with even more smartphone accessories in the works that are currently under wraps.

You can see some examples of celebrities showing off their PopSockets below:

Gigi Hadid was one of the first celebrities to sport a PopSocket, contributing to the gadget's popularity in Hollywood.

throwback #emo##emo#... @ gigihadid

Last summer, Jared Leto snapped a mirror selfie with his PopSocket.

#emo##emo#... @ jaredleto

The Dodgers were one of the first teams to unofficially endorse the gadget.

Coffee run! <a href="http:/... @ Los Angeles Dodgers

The trend has even caught on among Olympians: Last year, Michael Phelps took a photo with his wife and newborn baby Boomer.

Freezing moments in time wh... @ mrs.nicolephelps

Emma Roberts posted a Snapchat wielding a PopSocket as she got ready for the Coach 75th anniversary runway party in December 2016.

Model and reality TV star Nicole Williams is a PopSocket fan.

Come and knock on our door ... @ justtnic