Audi RS3 Fog Light Bulb Size

Audi RS3 rear fog light uses an H21W bulb size for replacement. The chart covers 2023 to 2024 model years with corresponding bulb size specifications.

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

Rear Fog Light

Years	Bulb Size
2023-2024	H21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BAY9s base. 12V, 21W.	H21W

Other Locations

Additional Notes

The H21W is the bulb type specified for the Audi RS3 rear fog light across the 2023-2024 model years.
The H21W operates on a 12-volt electrical system and draws 21 watts, which is standard for rear fog light applications requiring high visibility output.
This bulb uses a BAY9s base, a bayonet-style fitting with offset pins that prevent incorrect installation by ensuring the bulb can only be seated in one orientation.
The H21W is a single-filament bulb, meaning it serves one lighting function only, consistent with its dedicated rear fog light role.
The H21W is governed by ECE regulations, a standard recognized across Europe and numerous other markets worldwide, reflecting the regulatory framework under which the RS3 is certified.