Cheaper look-alikes have been around for years, but social media has made them more popular. Dupes can move into shaky legal territory if concerns arise around consumer confusion or patented designs.

Lululemon is suing Costco, alleging the wholesale retailer knowingly sold knockoff versions or dupes of its popular products.

Lululemon, a premium athleisure company based in Vancouver, Canada, filed its lawsuit against Costco on June 27 in California. The complaint, according to CBS News , alleges that Costco “unlawfully traded” on Lululemon’s “reputation, goodwill and sweat equity” by selling unauthorized knockoffs, infringing on the companies patents