Is it safe to mount the balasts within the headlight unit?This leads us onto fitting.
Whether you decide to mount the ballasts in the engine bay, or inside the light unit is your choice. The obvious difference being that inside the light unit will keep the engine bay that little bit tidier, and will prevent you from having to cut a hole in the back covers of the lights. If you decide to mount them inside the light unit you will need "Slim" ballasts as mentioned above.
The wiring is very simple, although it can look daunting. The wires are normally colour coded to each other which you connect before putting the kit into the car. The spade connectors wire into the plug from the original bulb.
Here is some pictures to show how the inside of the light unit looks with everything inside. The red square is where the ballast is placed.