The concession line was the place to be at the Lenovo Center on May 2. Fans rushed to shell out for the viral 28-ounce beer-skate mug: $19 each, or $12 plus the cost of a beverage.

The venue sold out of the souvenir cup instantly: 4,687 pieces, according to WFAN. That’s more than a quarter of the attendance for the game. It won’t return this season, and fans are reselling them for hundreds of dollars.

Jerseys, hats, and foam fingers have long been the fan merch of choice. Increasingly, though, to mark their game-day experiences, spectators are buying alcohol—because they want the souvenir cup it comes in.

The signature vessel is not new—think the coveted cup from the Kentucky Derby’s mint julep (some of which are 24-karat gold plated). The craze goes well beyond sports, like McDonald’s or Disneyland collectibles that date back decades. But social media has turned the keepsake into a status symbol at both one-off and multiday events.

“As these tournaments become higher profile, you want to be seen. So what do you want to be seen holding?” says Sandeep Satish, CCO of food and hospitality company Levy Restaurants. “Not only can we have a signature cocktail that’s approachable, easy to sip and fun, but the collectible nature of it has become, honestly, just as important.”