Audi RS3 Brake Bulb Size

The Audi RS3 brake light utilizes a P21W bulb size for the lighting system. Data for the specific component covers the period from 2023 through 2024.

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

Bulb Size by Year Range

Years	Bulb Size
2023-2024	P21W

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

The P21W is the brake bulb type specified for the Audi RS3 across the 2023-2024 model years.
The P21W operates at 12 volts with a 21-watt output, placing it in the standard single-filament signalling category used widely in automotive lighting applications.
As a single-filament bulb, the P21W serves dedicated functions such as braking, rather than combined stop/tail duties, which require a dual-filament design.
The P21W uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin offset, distinguishing it from the dual-contact BA15d base used in other bulb types.
The P21W carries ECE certification, meaning it conforms to the United Nations Economic Commission for Europe lighting regulations recognized across European and numerous worldwide markets.
The BA15s base of the P21W is not interchangeable with dual-contact BA15d bulbs, as the contact configurations are physically and electrically distinct despite sharing the same 15mm base collar.