Mercedes-Benz SLK250 Back Up Light Bulb Size

The Mercedes-Benz SLK250 back up light requires a bulb size of 921 for proper installation and function within the rear lighting assembly. Available data for the specified component covers the range from 2012 through 2015.

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
2012-2015	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The Mercedes-Benz SLK250 uses the 921 bulb for the back up light position across the 2012-2015 model years.
The 921 is a wedge-type bulb, classified under the T15 designation, which refers to its tubular glass envelope measuring 15 eighths of an inch in width.
Wedge bulbs are named for their base design, where the glass envelope itself is pinched into a wedge shape that locks directly into the socket without a separate metal base or pins.
The 921 operates at 12 volts and draws 16 watts, which is consistent with standard automotive low-current accessory circuits.
The 921 bulb conforms to ANSI standards, meaning its physical and electrical specifications are governed by the American National Standards Institute, ensuring consistent production across manufacturers in the United States and Canada.
Because the 921 is an ANSI-standardized part, bulbs carrying that designation from different manufacturers are generally interchangeable in terms of fit and electrical load.
The T15 wedge form factor is shared by several ANSI bulb numbers, so substitution with a visually similar wedge bulb of a different designation risks a mismatch in wattage or voltage rating.