This site explains everything you ever wanted to know about bulbs! (and conversions, wiring, relays, blue bulbs, etc)
It says that HB2, 9003, and H4 are essentially the same, that the HB2 is an H4 "built to tighter tolerances". Hope this helps.
[Edited by JCE on 01-23-2001 at 11:57 PM]
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E