If you’ve been on social media recently, you’ve seen these clogs.

Birkenstock Boston-style shoes have been flying off the shelves faster than they can be restocked, making them a hot commodity that can go for a high price among resellers.

Taupe, Suede Leather Boston Clogs seem to be the most popular and the hardest to find.

Because they’re hard to find, resellers on Poshmark and other platforms have charged as much as double the price listed on Birkenstock’s website of $155, per The New York Times.

Just one day ago, the Times reported that very few sizes are available, if any at all. On Birkenstock.com, more men’s sizes are available than women’s. Other resellers, such as Nordstrom and Journeys, have been known to run out of stock quickly, too.

One TikToker named Annie Paventy described the clogs as the “perfect trifecta” of versatility, comfort and trending on Pinterest and TikTok.

On the post, there were some who complained that walking long distances is not a good idea. To break in the shoes, Birkenstock recommends in its fitting guide to put a finger between the shoes and your heel and toes and flex the foot to “initiate the break-in period.” The company also recommends only wearing the shoes for a few hours the first six times.

The clog shoe is by no means new to the market and has been sold by Birkenstock since 1979, according to Forbes, and throughout the years has made appearances in trending fashion, per Vogue.

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Most recently, Kendall Jenner and YouTuber Emma Chamberlain caught onto the trend.

Since these were most popular at the beginning of the century — per Forbes — and with the current emphasis on ’90s style, it’s no wonder that the clogs are back.