Like nitro said, H7 for the low beam if your car don't have hid already. You can just simply buy a capacitor off your local electronic store, fry's or radio shack, and it is cheap. My friend did it to his 330i few months ago, and it held up fine. Go search for e39/e46 hid on google, and there should be some write up on the installation of hid, and which capacitor to use.