In the 986 halogen (non litronic/xenon) system of a 986 - hi, low and fog all use H7 bulbs. There is also a 'city light' in the low beam housing. That being said, the bulbs are opposite of their name in the housing, high beam is below the low beam.
To answer what I think is your question about replacing both the low and hi beam H7 bulbs in one housing? Not necessary. However, you may want to replace the same bulb on the opposite side of the car as they usually burn out w/in a week or two of each other unless you know of a reason one side prematurely went out.
In a pinch, if you don't have a spare new bulb around, you can rotate one from either the hi or fog to the low as needed.
