ST. LOUIS (KTVI) — Want a free burger? White Castle is celebrating National Slider Day on Wednesday by offering customers … you guessed it, a free slider.

Customers can redeem this offer on May 15 using a digital coupon from White Castle’s social media or by entering the code SLIDERDAY on the app with no purchase required.

“We’re humbled to have always led the charge to serve up hot and tasty food at an affordable price,” states Jamie Richardson, vice president at White Castle. “Today when families follow their Crave to the Castle, no matter their income, they know they are going to be able to explore a delicious menu they can afford. It’s a testament to how we’ve helped create memorable moments for generations of customers.”

White Castle introduced National Slider Day in May, 2015.

With its founding in 1921 in Wichita Kansas, White Castle, touted as “America’s first fast-food hamburger chain,” introduced its 5-cent Original Slider, selling them by the sack, according to the burger chain.

The Slider’s iconic 2-by-2-inch patty is 100% beef and “steamed-grilled on a bed of onions.”

In 2014, Time magazine declared the White Caste Slider “the most influential burger of all time.”

“The only thing better than polishing off a Sack of Sliders alone, is doing it with friends,” the chain said on its website.