Automotive Reference
What H11, 9005, H4 and the rest actually interchange with — and the trap that "similar base" doesn't always mean you can swap them. The base and tabs decide the fit.
A bulb is named for its base — the collar, locking tabs and connector that key it into the housing. Same base family usually means it physically fits.
Bulbs on the same row share a base family and usually interchange physically. Read the warning below before you assume they're electrically identical.
| Bulb | Interchanges / also known as | Base | Typical use |
|---|---|---|---|
| H11 | H8, H9, H16 (same family) | PGJ19-2 | Low beam · fog |
| 9005 | HB3, H10, 9040, 9145 | P20d | High beam |
| 9006 | HB4, 9012 | P22d | Low beam |
| H4 | 9003, HB2 (dual filament) | P43t | Hi + low in one |
| H7 | — (mostly its own) | PX26d | Low or high |
| H1 | — | P14.5s | High beam · fog |
| H3 | — | PK22s | Fog |
| 880 | 884, 885, 890, 893 | PGJ13 | Fog |
| 9007 | HB5 (dual filament) | PX29t | Hi + low in one |
Same base family (PGJ19), so they physically fit the same socket. But H8 and H16 are lower wattage and H9 is higher, with different beam focus. They interchange mechanically; whether they're right depends on the housing. H11 is the common low-beam/fog size.
9005 (HB3) is a high-beam bulb; 9006 (HB4) is low-beam and a bit lower wattage. They use different bases and are not interchangeable — a very common mix-up. Many cars use a 9005/9006 pair.
An H4 is a single dual-filament bulb that does both high and low beam (common on older/single-bulb headlights). An H7 is single-filament — cars using them have a separate bulb for high beam. Different bases; not interchangeable.
If the base matches (say an LED "H11"), it fits. But beam pattern, glare, CANbus error codes and local legality vary a lot — a cheap LED in a halogen reflector often dazzles oncoming drivers without lighting the road better. Check the housing type and your local rules first.