The Mercedes-Benz CLK55 AMG tail light requires bulb size P21/4W or 12821 depending on the specific application. Data for the provided components covers the range from 2001 through 2005.
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 outer tail light specifications reference three distinct bulb types across the listed model years: P21/5W, P21/4W, and two Philips-numbered T10 wedge bulbs (12961 and 12821).
P21/4W is the most frequently specified bulb across the CLK55 AMG outer tail light positions, appearing across multiple years and positions in the data.
The P21/4W is an ECE-standard dual-filament signalling bulb rated at 12V with a 21W main filament and a 4W secondary filament. It uses a BAZ15d bayonet base, which is an offset-pin fitting designed to prevent incorrect installation.
The P21/5W differs from the P21/4W in both its secondary filament rating (5W versus 4W) and its base type. The P21/5W uses a BAY15d bayonet base, while the P21/4W uses a BAZ15d base. These two base types are not interchangeable.
The 2006 Mercedes-Benz CLK55 AMG outer tail light specifies the P21/5W, making it the only model year in the listed data to require this bulb type in that position.
Philips part numbers 12961 and 12821 both describe T10 miniature wedge bulbs sharing the same W2.1x9.5d base, 12V rating, and 5W output. Despite their identical electrical and physical characteristics, they carry separate part numbers within the Philips catalog.
The BAZ15d base of the P21/4W and the BAY15d base of the P21/5W are physically distinct bayonet fittings. Substituting one for the other is not possible without a matching socket.
The T10 wedge bulbs specified (12961 and 12821) are single-filament units, in contrast to the dual-filament P21/4W and P21/5W types also present in the specifications. This indicates different functional roles within the tail light assembly.