Just like those practical Velcro straps, the on-going popularity of the Teva sandal seems to be tenaciously sticky.

Launched in the 1980s by Grand Canyon river guide Mark Thatcher, the sandal was initially designed to stay on feet during water sports and targeted towards outdoor adventurers seeking comfortable sandals. But in recent years, a rising trend of nomcore and “ugly-chic” footwear, a category in which Birkenstocks also fall into, has taken the sandals from what was arguably thought of as a fashion faux pas, to being included in high end fashion shows and designer look books. And that’s when Teva, in particular, began capitalizing on its new-found trendy status.

“The high-end Teva trend really started back in 2014 when Marc Jacobs and Prada showed versions on their runway,” said Diana Tsui, the Cut’s senior fashion market editor. “Teva caught on and collaborated with Opening Ceremony.”

Teva has taken advantage of this newfound attention, and, thanks to a smart network of fashion partnerships, influencer collaborations and a strong social presence, it has managed to maintain the momentum.

Through a collaboration with San Francisco-based agency Heat last summer, the brand used media partners like Nylon magazine and WhoWhatWear, as well as fashion bloggers at music festivals to susrface the brand and target a new demographic of younger, fashion-forward customers.

Today, Teva’s Instagram page, with 114,000 followers, is rich with images of adventure and wilderness, featuring photos of its shoes on the feet of people on pristine beaches, lakeside, in kayaks, and on mountain tops. Fashion retailers like Open Ceremony and Nasty Gal also began carrying trendy versions of the sandals.

The push has kept the buzz lasting longer than a single season, too. Designer Lou Dalton, for example, featured a Teva and sock combination in her Spring/Summer 2017 collection at London Men’s Fashion Week this year, and contemporary brand Opening Ceremony has renewed its partnership with Teva for the third year in a row. In June, the brand also announced its first celebrity collaboration with R&B singer and songwriter Jhene Aiko, for three different styles of sandals.

“Sport inspired sandals were all over the Spring 2016 runways,” said Rachael Wang, Allure’s fashion director. “From Chanel, Ferragamo, and Burberry to Michael Kors and Kenzo.” One of the factors driving the more casual and comfortable approach to footwear is the increasing number of people working from home, which Wang said will continue to underpin the popularity of Teva and Birkenstock sandals for seasons to come.

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Lou Dalton’s Spring/Summer 2017 Menswear show.

Birkenstock sandals’ own new peak in popularity came the year before the Teva craze, and it was Celine’s Spring 2013 show that put Birkenstocks on the fashion map, according to Racked’s editor in chief, Britt Aboutaleb. “The ugliest shoe in the world was suddenly the most chic,” she said, with designers from Givenchy to Isabel Marant designing their own versions of the shoe.

Unlike Teva, however, when Birkenstock’s popularity saw an uptick, the brand didn’t refresh its look, change its advertising and marketing strategies, or try to position itself in front of a new group of consumers, said the brand’s U.S director of communications, Matt Hundley. Founded in 1774 and family owned, the brand doesn’t release revenue or sales percentages, but Hundley said it’s that history people resonate with. “The product you see today is what you saw 50 years ago and I don’t know how many companies can say that.”

While most brands are focused on building a voice and presence on social media, Birkenstock has taken a light approach. Its Instagram account, with 110,000 followers, started just under two years ago and only  has 29 posts; its U.S. Twitter account, with just more than 4,000 followers, last posted in 2014.

With fall just around the corner, the “ugly” style of sandals safely survived another summer, but how much longer they’ll remain popular for remains unclear.

“I expect Tevas and Birkenstocks to remain popular for at least another year, out of sheer comfort alone,” said Tsui. “But editorials will shift in focus to include more streetwear (Vetements) and maximalism (Gucci).”