They are, in effect, single filament bulbs, so they are low beam or high beam, depending on the location they are used on the particular vehicle. With low beams on, only the outer 2 bulbs are powered. With high beams on, all 4 bulbs are powered. The low beams are well controlled and aimed wide at the road, while the inner high beams are blasting way down the road. They work quite well in this configuration.