The Lexus RX300 brake light utilizes a 7443 bulb size for illumination across all listed vehicle applications. Data provided for the specific component covers the range from 1999 to 2003.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Lexus RX300 uses two distinct bulb types across its brake lighting system for the 1999-2003 model years: the 7443 and the 921.
The 7443 is a dual-filament wedge bulb in the T20 form factor, rated at 12V with a 21W/5W output, and meets ANSI standards for the US and Canada markets.
The dual-filament design of the 7443 allows it to serve two brightness levels within a single bulb, which is typical for brake and tail light positions that share the same housing.
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 T20 and T15 designations refer to the wedge base size of each bulb, and these two sizes are not interchangeable despite both using a wedge-style base.
The 7443 is specified for the brake, inner brake, and outer brake positions on the Lexus RX300 across all five model years covered.
The 921 is specified exclusively for the Center High Mount Stop Light position across the full 1999-2003 range.
Because the 7443 and 921 share a wedge base style but differ in size and filament count, substituting one for the other in any of the RX300 brake light positions would result in an incorrect fitment.