DOUBLE HIGH BEAMS: So you already have a halogen high beam? When retrofitting a bi-xenon projector; you can harness the stock high beam power to activate the bi-xenon solenoid at the same time, thus doubling your high beam output.
QUAD RETROFITS: Use a splitter to run two low beam harnesses in parallel for four ballasts and then activate two pairs of bi-xenon solenoids off a single high beam output. Three total splitters needed.
ALL FITMENTS: For the input, make sure to select the size that matches with your stock high beam bulb type. The output will generally be the female version of that same bulb, coupled with a 9006 to plug into your bi-xenon projector solenoid.