The Lexus RC300 back up light requires a bulb size of 921 for the specific lighting component located at the rear of the vehicle. Data for the bulb specifications covers the range from 2016 to 2018.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 921 bulb is the sole bulb size specified across all listed back up light positions on the Lexus RC300, covering model years 2016-2018 for the standard back up light and 2016-2019 for the inner back up light.
The 921 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are governed by a recognized North American industry standard applicable in both the United States and Canada.
The 921 uses a wedge-style base, designated T15, which refers to a tubular bulb body approximately 15 eighths of an inch wide that is held in its socket by friction rather than by pins or a bayonet mechanism.
The 921 operates at 12 volts and consumes 16 watts, values consistent with standard automotive electrical systems.
The T15 wedge base format of the 921 means fitment depends on socket compatibility with that specific base type, and substituting a bulb with a different base style would not physically seat correctly even if the voltage rating matched.
The inner back up light position on the Lexus RC300 carries a 2019 model year entry that the standard back up light position does not, indicating the two positions are treated as distinct fitment categories within the specifications.