Audi R8 Back Up Light Bulb Size

The Audi R8 back up light requires a specific H21W bulb size for proper installation and function. Data for the bulb size covers the range from 2008 to 2012.

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
2008-2012	H21W

Bulb Specifications

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

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Additional Notes

The Audi R8 uses the H21W bulb for the back up light position across the 2008-2012 model years.
The H21W is an ECE-standard bulb, meaning it conforms to the Economic Commission for Europe regulatory framework used in European and worldwide automotive lighting applications.
The H21W operates at 12 volts and consumes 21 watts, which is typical of a single-filament incandescent signalling bulb.
A single-filament design means the H21W serves one lighting function only, as opposed to dual-filament bulbs that handle two functions such as stop and tail from a single unit.
The H21W uses a BAY9s base, which is an offset bayonet mount. The offset pin arrangement prevents incorrect installation by ensuring the bulb can only be seated in one orientation.
The BAY9s base is specific to the H21W and is not interchangeable with the more common BA15s or BAY15d bayonet bases found in other automotive signalling bulbs, making socket compatibility a relevant fitment consideration.