But typically, you can squeeze two to three cards into a phone card holder. How many cards you’ll be able to hold depends on the thickness of the cards you’re adding. Once you’ve narrowed your choices to the card holders that will stick to your phone, you’ll need to take a look at the pocket design that works for you.

Many manufacturers use adhesive from 3M, maker of Post-It Notes, but there are competing products that can provide similar results. You’ll need a holder with adhesive strong enough to stay in place, but it can’t be so strong that it damages the back of your phone. The adhesive used to attach the holder is also important, especially if you’re putting it directly on the back of your phone rather than on a case. But it’s important to make sure each of those pockets is designed to prevent your cards from falling out, whether that means nonslip material or a tightness that keeps your cards in place.

You can find a wide variety of designs along with different pocket options to fit various preferences. In fact, these adhesive card pockets have become so popular in recent years, they’ve evolved far beyond the basic versions you could initially buy. They’re perfect for keeping up with your ID cards at the gym, while out with friends or even for everyday use.

But phone card holders aren’t just for college students. Instead of carrying a purse or wallet, they can simply stick their IDs and payment cards in a pocket on the back of a smartphone and head to class.

Phone pocket holder