The Mercedes-Benz SLK230 front side marker bulb uses 12961 or 12821 size, while the rear side marker bulb uses 67 or 12821 size. The replacement chart covers 1998 to 2004 production 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.
The T10 wedge bulb is the most frequently specified type across the Mercedes-Benz SLK230 side marker positions, appearing in both front and rear locations across the majority of model years covered.
Two Philips part numbers, 12961 and 12821, both describe a T10 miniature wedge bulb with a W2.1x9.5d base rated at 12V and 5W, making them electrically and physically equivalent despite carrying different part numbers.
The W2.1x9.5d base designation refers to a wedge-style connection where the glass envelope itself acts as the retention mechanism, requiring no separate metal base to lock into the socket.
The Mercedes-Benz SLK230 front side marker uses bulb 12821 for model years 2000-2003, while the 1998, 1999, and 2004 model years use bulb 12961 instead.
Because 12821 and 12961 share identical base type, voltage, and wattage ratings, the front side marker socket accepts either part number without modification across all listed model years.
The rear side marker of the Mercedes-Benz SLK230 uses bulb 12821 for model years 1998-2003, while the 2004 model year specifies the entirely different bulb 67.
Bulb 67 uses a BA15s single-contact bayonet base, which is physically incompatible with the W2.1x9.5d wedge socket used by the 12821 and 12961 bulbs, making the 2004 rear side marker socket a distinct fitment from all other listed positions.
The BA15s bayonet base on bulb 67 features a single contact pin offset to one side, a standard configuration that allows only one rotational orientation during installation.
At 8W, bulb 67 draws more power than the 5W T10 bulbs specified elsewhere in the SLK230 side marker positions, meaning the two bulb families are not interchangeable even where a socket adapter might otherwise allow physical fitment.
Bulb 67 is classified under the ANSI standard used in the United States and Canada, and it is described as a lower wattage variant of the 1156, which shares the same BA15s bayonet base but operates at a higher wattage.