The Audi RS5 front turn signal requires a 12174NA bulb size while the rear turn signal uses a 921 bulb size. The replacement chart covers 2013 through 2015 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Audi RS5 uses two distinct bulb types across its front and rear turn signal positions for the 2013-2015 model years: the 12174NA for the front and the 921 for the rear.
The 12174NA is an OEM part number rather than an ANSI industry-standard designation, meaning it is a manufacturer-specific reference tied to original equipment fitment.
The 12174NA features natural amber glass, which produces the amber color required for turn signal use through the glass itself rather than through a colored lens or coating.
The 12174NA operates at 12 volts, consistent with standard automotive electrical systems.
The 921 carries an ANSI standard designation, indicating it conforms to a standardized specification recognized across the United States and Canada.
The 921 is a T15 wedge-type bulb, meaning it uses a wedge base rather than a bayonet or screw base, and the T15 designation refers to its tubular envelope width of 15 eighths of an inch.
The 921 operates at 12 volts and a power rating of 16 watts.
Because the front position specifies the OEM-designated 12174NA while the rear specifies the ANSI-standard 921, the two positions are not interchangeable with each other despite both operating at 12 volts.