Lululemon is suing Costco, accusing the discount retailer of selling “confusingly similar” replicas of its jackets, sweatshirts and pants.

In a lawsuit filed Friday in the U.S. District Court for the Central District of California, the athletic and lifestyle apparel company claims that certain Costco products imitate its own designs so closely that it constitutes “trade dress” infringement, which occurs when a product mimics another so closely that it confuses consumers.

The apparel company claims that Costco’s “knockoff” designs, or product “dupes,” violate trademark law because “some customers incorrectly believe these infringing products are authentic Lululemon apparel.” In other cases, “customers specifically purchase the infringing products because they are difficult to distinguish from authentic Lululemon products,” the lawsuit alleges.

“Indeed, one of the purposes of selling ‘dupes’ is to confuse consumers at the point-of-sale and/or observers post-sale into believing that the ‘dupes’ are Plaintiffs’ authentic products when they are not,” the lawsuit alleges.