Also placed in a well designed housing such as the ECE or DOT spec housing lamps (as recommended by 240Hoke) really makes sense to me. I realized the Ebay drop in housings don't really do justice. Getting a good housing that is spec'd also helps the beam cutoff as to not distract other drivers as well.
Examples of some E Code housings below... As you can see what a lot of the guys are referring to the step on one side is higher to illumiate pedestrians, street signs, and to not distract drivers. Making sure the correct lens (projector housings, or bulb housings) installed on the correct side according to your driving side (RHD or LHD) is also key to doing things the right way.
LHD E-Code Housing
RHD E-Code Housing