Do these mount at the factory headlight locations?

Yes — these use the stock mounting points. No drilling or bracket fabrication required.

What bulb type do these take?

Confirm bulb fitment with your original housing spec or consult your W126 service manual, as bulb compatibility depends on the specific headlight design.

Are these sealed units or can they be serviced?

These are complete sealed headlight assemblies. Internal service is not recommended — if fogging or failure occurs down the road, replacement is the standard fix.