These projectors are perfect for retrofitting H4/9003 halogen headlights with their included adapter plates, allowing a "plug n play" type installation with no cutting/modification to the housing, and an instant horizontal alignment. Note that they're not limited to H4/9003's – but are ideal for them.
Disassemble headlights, insert threaded mounting shaft of the Mini D2S through the pre-existing hole in the back of your reflector bucket, tighten the stack with the included hardware, and you're virtually done.