If you’re hoping to grab a pair of UGG classic ultra mini platform boots, you’re going to want to pack your patience.

The sheepskin, shearling-lined boots with a 2-inch platform base is an updated twist on the early 2000s classic. They’ve become the hot-ticket item of the season for those wanting to stay warm while being fashionable.

The footwear runs for $150 and comes in black, chestnut and a green called forest night. On the UGG website, the only item available was a chestnut color in a size 9 in womens. For any other sizes or colors, customers are prompted to sign up for the waitlist.

They’ve “flown off the shelves,” an UGG spokesperson told The NY Post.

The hard-to-get booties have become profitable on secondary market sites. A pair of chestnut booties are going for up to $245 on StockX, while a pair of the black ones are going for $175. On eBay, they’re going for as much as $340.39.

The boots have gained popularity after being spotted on celebrities like Bella and Gigi Hadid, Kylie Jenner, Kaia Gerber, Elsa Hosk and Keke Palmer.

While some are waiting for the real thing, others are in search of dupes. Many on TikTok have become fans of U.K.-based Pretty Little Thing’s lower-priced version. Sophie Anne posted her purchase of the knockoffs that look almost identical. They run for £40, which is $47.54 USD.

A Chinese website called DHgate is selling lookalikes for up to $40.12. DSW is selling a dupe from the brand Bearpaw for $84.99.

UGG started in 1978 by Australian surfer Brian Smith. The boot was a fashion symbol for surfers throughout California by the mid-’80s. Since then the brand has expanded to the mainstream thanks to its popularity in the early aughts.