The Mercedes-Benz CLK55 AMG side marker utilizes a unique 12961 bulb size for the lighting assembly. Data for the specified vehicle covers the range from 2002 through 2002.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz CLK55 AMG uses two distinct bulb families across its side marker positions: the T10 miniature wedge type and the P-series dual-filament bayonet type, each serving different positions and model years.
The T10 wedge bulb uses a W2.1x9.5d base, which is a standardized miniature wedge base common in low-wattage automotive signal and marker applications. Both the 12961 and 12821 are Philips part numbers assigned to T10 bulbs rated at 12V and 5W.
Although the 12961 and 12821 share the same T10 form factor, W2.1x9.5d base, 12V voltage, and 5W rating, they carry different Philips part numbers, which can indicate differences in filament construction, glass envelope, or light output characteristics.
For the front side marker on the CLK55 AMG, the 2003-2006 model years use the 12961 bulb, while the 2001-2002 model years use the 12821 bulb.
For the rear side marker, the 2003-2005 model years use the 12961 bulb, placing it in both front and rear positions during that period.
The 2006 rear side marker position shifts to the P21/5W bulb, which uses a BAY15d bayonet base and carries a dual-filament 21W/5W rating, making it electrically and physically incompatible with the T10 wedge bulbs used in other positions.
The 2001-2002 rear side marker uses the P21/4W bulb, which features a BAZ15d bayonet base. The BAZ15d base is offset differently from the BAY15d base used by the P21/5W, meaning the two bayonet bulbs are not interchangeable despite their similar appearance.
The P21/5W and P21/4W are both ECE-standard dual-filament bulbs rated at 12V with a 21W primary filament, but their secondary filaments differ at 5W and 4W respectively, and their bayonet bases are mechanically distinct to prevent incorrect installation.
The rear side marker position on the CLK55 AMG uses three different bulb types across the 2001-2006 production span, meaning the rear position does not share a single consistent bulb specification across all years.
A T10 wedge bulb cannot be substituted into a bayonet socket, and a P21/5W cannot be substituted for a P21/4W due to the differing base offsets, making position-specific and year-specific bulb selection necessary for the CLK55 AMG.