The 350 knock-off Fitbit wristbands came from Hong Kong on Dec. 4, according to a CBP press release on Tuesday. “Working with the trademark holder, CBP determined that the 350 smart wristbands were counterfeit, and seized them on Jan. 4,” the agency said. Fitbit was not mentioned by name in release, but a photo of what the CBP seized makes it clear.

Based on the math and the photo, the wristbands look to be counterfeit Fitbit Flex activity trackers. Fitbit did not immediately respond to a request for comment from Fortune.

Counterfeit cell phones, smartwatches, LCD screens, and backup hard drives are all items that U.S. Customs agents have previously confiscated at Philadelphia’s port, but this latest seizure “seems to be the first time that CBP has encountered counterfeit Fitbits or similar smart wristbands here,” according to CBP public affairs officer Stephen Sapp.

Stopping counterfeit goods—products that infringe on intellectual property rights such as patents and trademarks—is something the CBP is focused on. The agency handled more than 23,000 seizures of IP-infringing items totaling $1.2 billion in retail value in 2014, according to its records. Apparel and related accessories along with consumer electronics were the most seized items that year.

U.S. Customs apparently has a good sense of humor as well, as Philadelphia Magazine noted. The headline on CBP’s release: “Philadelphia CBP Flexes Trade Enforcement Muscle.”

Fitbit (“FIT”), which went public last June, continues to dominate the wearable technology market: Its fitness trackers continue to outpace sales of smartwatches, as Fortune reported in December. Last week, however, Fitbit’s stock price fell after introducing a smartwatch of its own. And now Fitbit is facing a class action lawsuit alleging that the company’s heart-rate monitoring technology is inaccurate.