Mercedes-Benz C280 front and rear side marker bulbs utilize sizes 12961, 2357NA, P21/5W for front applications and 12821 for rear positions, with bulb specifications varying across the model line. The replacement chart covers 1994 through 2007 model years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz C280 rear side marker position uses the 12821 bulb across all model years listed in the specifications, from 1994 through 2007, making it the only bulb type with uninterrupted fitment across the entire rear side marker range.
Both the 12821 and 12961 are Philips part numbers designating miniature wedge bulbs of the T10 type, each sharing the same W2.1x9.5d base configuration and identical 12V, 5W electrical ratings.
Despite their shared base type and wattage, the 12821 and 12961 are specified for different positions on the C280, with the 12821 assigned exclusively to the rear side marker and the 12961 assigned exclusively to the front side marker for the 2006-2007 model years.
The front side marker position on the C280 shows a bulb type change across its model year range. The 1994-1996 years use P21/5W, the 1997-2000 years use 2357NA, and the 2006-2007 years use the 12961.
The 2357NA is an ANSI-standard dual-filament bulb rated at 12V with a high filament draw of 26.9W and a low filament draw of 8W. It uses a BAY15d bayonet base and features natural amber glass, which produces an amber output without the need for an amber-tinted housing.
The P21/5W follows the ECE standard used in European and worldwide markets. It is also a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments at 21W and 5W respectively.
Both the 2357NA and P21/5W share the BAY15d bayonet base, but their wattage ratings differ. The 2357NA high filament draws 26.9W against the P21/5W high filament of 21W, which means the two types are not electrically interchangeable despite the shared base format.
The BAY15d base used by both the 2357NA and P21/5W is an offset-pin bayonet design, where the two pins are positioned at different heights to prevent incorrect installation of a single-filament bulb in a dual-filament socket.
The W2.1x9.5d base designation on the T10 wedge bulbs refers to a wedge-type contact system with no separate metal base pins, relying instead on the contact strips along the sides of the glass envelope to complete the circuit within the socket.
The front side marker socket on the C280 accommodated three distinct bulb types across the listed model years, each from a different standard or manufacturer classification, indicating that direct substitution between years requires verification of both base type and wattage compatibility.