D1S 35W Philips XenStart A715 OEM 43K bulb DOT 06J Mostly used in the automotive world today by manufacturers like Audi, Mercedes Benz, Lexus, and BMW, VW and Porche etc.. Sold individually 1 bulb. Bulbs and Ballasts are non-returnable, non-refundable, so make sure you are ordering the correct part for your car. Bulb or ballast?: see More How do I tell if my bulb is bad? Or is my ballast bad? The ballast is a small electronic box that powers the bulb. Remove the good bulb and install it on the non-working side. If the bulb works, the bulb that was on that side is defective. If the good bulb does not work on this side, the ballast is defective and you will need a new ballast.