The Mercedes-Benz C350 side marker requires a bulb size of 12961 for the exterior lighting system. Data for the specified component covers the range from 2008 through 2011.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz C350 uses the 12961 bulb for the front side marker position across all model years in the specifications, spanning 2006-2015.
The rear side marker position on the C350 uses two different Philips part numbers depending on the model year. The 12821 is specified for 2006-2007, while the 12961 takes over from 2008-2015.
Both the 12961 and 12821 are Philips part numbers designating miniature wedge bulbs built on the T10 form factor with a W2.1x9.5d base.
The W2.1x9.5d base is a wedge-type base where the bulb glass itself acts as the contact point, requiring no separate metal pins or bayonet fittings for retention.
Both bulbs operate at 12 volts and 5 watts, placing them in the low-wattage category typical of side marker and parking light applications.
Despite carrying different Philips part numbers, the 12961 and 12821 share identical electrical and physical specifications, including voltage, wattage, base type, and bulb form factor.
The T10 designation refers to a tubular bulb with a nominal width of 10 millimeters, a standard sizing used widely across automotive side marker and interior lighting positions.
Because the 12961 and 12821 are physically and electrically identical, the part number difference reflects a Philips catalog distinction rather than a functional or fitment difference between the two bulbs.