Does anyone know why the car manufacturers make different headlight bulbs for different headlights? Why don't they make one size fits all instead of H1, H4, H7, ect. All of the xenon headlamps have the same size respectively. Just curious.

 

Sometimes it depends on the headlight design, for instance smaller headlights use 9004 bulbs because they are dual-filament and can do high/low while larger headlights have different chambers for the high and low. Then there is available space behind the bulb, 9006/9005 such bulbs have an elbow to allow the connector to head down/up across the housing instead of coming straight out so save an inch or two. Things like that I would assume.

-tc

 

ehh, its 9003 and 9007 bulbs that are bi-filament

 

So why not make one light bi-filament. Why the need for two. I know that the manufactures have to make an allowance for space availabity when considering headlights but that still does not require the need for different housings. IMO. Why the need for a 9007 and a 9005? Are they not both for the high beams? Do they not both have the same kind of receptacle? They both have the insert and turn lock in mechanism inside the headlight housing. Why the need for two different bulb types?