Aside from National Doughnut Day, National Flip Flop Day is also a real thing.to celebrate, Tropical Smoothie Cafe is doling out free “sunshine smoothies” in a 20th-anniversary cup on National Flip Flop Day. All you have to do is bear your lower digits in one of its 500 U.S. locations.

The free 16-ounce smoothies which “capture the taste of summer,” will be available on Friday, June 16th, from 2:00 pm to 7:00 pm.

“It’s been over 10 years since we started National Flip Flop Day to show appreciation for our guests and mark the kick-off to summer,” said Mike Rotondo, CEO of Tropical Smoothie Cafe.

The company’s sunshine smoothie blends orange, orange juice, banana, pineapple, and mango and, best of all, it’s free if you show your manicured, mangled or fungal toes in flip flops.