the part no. i gave you are for the "projector lights" the new style for the headlights from the 2003 ml500, xenon hid is something totally different, have you ever seen a mercedes, audi, drive past you and there lights are blueish tint color and blinds you? that is called HID or XENON.. you can buy them seperately.. i have both, first I got the projectors, than i installed the HID bulb and ballast after, the hid kit alone can costs $1,000 its not cheap.. and yes you loose the foglights but i have the xenon lights is so bright the fog lights are useless and i believe you still get the rear foglights.. you can get the xenon bulbs for your car using your old projector headlights assemblies.. but of course the new projectors are more attractive!