Lexus IS300 Brake Bulb Size

The Lexus IS300 brake light utilizes a 7443 bulb size for the specific lighting component located at the rear of the vehicle. Data for the bulb specifications covers the 2001 through 2001 range of production.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Center High Mount Stop Light

Years	Bulb Size
2023-2024	194
2001	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T10). 12V, 3.78W.	194
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The 194 bulb is an ANSI-standard miniature wedge type with a T10 form factor, rated at 12V and 3.78W. It serves as the Center High Mount Stop Light on the Lexus IS300 for the 2023-2024 model years.
The 921 bulb is an ANSI-standard wedge type with a T15 form factor, rated at 12V and 16W. It fills the same Center High Mount Stop Light position on the 2001 IS300.
Although both the 194 and 921 are wedge-style bulbs operating at 12V, their wattage ratings differ substantially. The 921 draws 16W compared to the 194's 3.78W, making the two types non-interchangeable despite sharing a general wedge construction.
The T10 and T15 designations refer to the outer width of each bulb's glass envelope, expressed in eighths of an inch. The T15 of the 921 is physically larger than the T10 of the 194, which further prevents cross-fitment between the 2001 and 2023-2024 specifications.
Both bulb types carry ANSI standardization applicable to the US and Canadian markets, meaning replacements sourced from those markets are expected to conform to the same electrical and physical tolerances defined by that standard.