Originally Posted by Zeichen311

Hmm. I'm not sure. That may be an update for the F30; I don't recall that from my E90's winter mat set (though it's been a couple of years, I may have forgotten).

I would say it's probably scrap also, but it could be some kind of anchor to secure the rear mats in the car. Just in case, look at the underside of the front seats, above the rear footwells. If you don't see an obvious fixture to which the hanger would attach--it would be very obvious--then I'd say it's safe to remove & discard.