On both high and low beam.
Previous owner put it in. Light output is excellent especially compared to OEM lights.
I had to replace main light recently (25euro ) after a year or two of use.
Installation is not that hard with these mini ballasts/boosters. You just screw them to the headlight subframe and find place for all the cables.
Thing is, the kit is expensive, the lights are fragile and it's quite tiring to get it to trow the light where you need it. I'm still fiddling with mine and still not completely happy.
Search the forum for 'Osram'. I've read positive things about some of theirs light bulbs.
Welcome aboard Macc. Step one is to adjust your OEM head light a little higher. It seems the V comes through too low. Next up would be a high performance Halogen lamp. Much cheaper and easier and I bet it does the trick. There are many posts on the subject.
You can use the car kit with 2 H7 bulbs to replace both high and low beam. I also recommend the slim ballasts so you can fit them easier. Looks like they are on sale now for $35 for the car kit. I didn't get my 250 bulbs from them, but I have ordered from them before for my dad's truck. Shipping took a little while, but good price is worth the wait I think.