H13 HID Bulbs are dual filament HID replacement bulbs. The bulbs are sold in a pair (2 pieces) and come is two variation. You can either choose the standard H13 High/Low bulbs which give you HID Lights on your low beam only or you can upgrade to the H13 Bi-Xenon bulbs which will give you HID Lights on both your low beams and high beams.