The INFINITI M45 brake light requires a 7443 bulb size for the specific lighting assembly. Data for the bulb requirements covers the period from 2003 through 2004.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The INFINITI M45 uses the 7443 bulb for brake lights across the 2003-2004 model years.
The 7443 is a dual-filament wedge bulb in the T20 form factor, rated at 12V with a 21W/5W output, conforming to ANSI standards for the US and Canada markets.
The dual-filament design of the 7443 allows it to serve two distinct brightness levels within a single housing, which is why it is suited for combined stop and tail light functions.
The center high mount stop light on the INFINITI M45 uses the 921 bulb for the 2003-2004 model years.
The 921 is a single-filament wedge bulb in the T15 form factor, rated at 12V and 16W, also conforming to ANSI standards for the US and Canada markets.
The T15 form factor of the 921 is physically smaller than the T20 form factor of the 7443, meaning the two bulbs are not interchangeable despite both being wedge-base types.
The wattage difference between the 7443 (21W/5W) and the 921 (16W) reflects their separate roles, with the higher-wattage filament of the 7443 dedicated to the primary brake stop signal.