Mercedes-Benz SLK55 AMG Back Up Light Bulb Size

The Mercedes-Benz SLK55 AMG back up light utilizes 921, P21W, and 1156 bulb sizes depending on the specific version. Data for the bulb sizes covers the range from 2005 to 2016.

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
2012-2016	921
2005-2010	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The Mercedes-Benz SLK55 AMG uses two distinct bulb sizes for the back up light across its model years: the 921 and the 1156, both of which conform to ANSI standards applicable in the US and Canada.
The 921 bulb is a T15 wedge-type unit operating at 12V and 16W. Its wedge base design means it is inserted directly into a socket without a separate locking mechanism.
The 1156 bulb is a single-filament type with a BA15s bayonet base, operating at 12V and 21W. The BA15s designation indicates a single-contact bayonet fitting with a 15mm base width.
The 1156 draws 21W compared to the 921 at 16W, reflecting a difference in power consumption between the two bulb types used across the SLK55 AMG's production span.
The Mercedes-Benz SLK55 AMG uses the 921 bulb for model years 2012-2016, while the 1156 bulb applies to model years 2005-2010.
The two bulb types are not interchangeable. The 921 uses a wedge base and the 1156 uses a bayonet base, meaning the socket design differs between the earlier and later model year groups.
Because the base types are physically incompatible, a bulb specified for a 2005-2010 model year cannot be fitted into the socket of a 2012-2016 model year without modification, and vice versa.