Mercedes-Benz SLK300 front turn signal bulbs use 3457NA size while rear turn signal bulbs use 12496 or PY21W size. The replacement chart covers 2009 to 2016 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 3457NA is the most frequently specified bulb across the Mercedes-Benz SLK300 turn signal data, appearing as the front turn signal bulb for the 2009-2011 and 2016 model years.
The 3457NA follows the ANSI standard used in the United States and Canada. It is a dual-filament T25 wedge bulb rated at 12V with a 27W main filament and a 7W secondary filament, and its natural amber glass produces the required amber signal color without a separate lens filter.
The 2016 Mercedes-Benz SLK300 front turn signal specifies the 3457NA exclusively for vehicles equipped with halogen capsule headlamps, indicating that this fitment is conditional on the headlamp type installed.
The rear turn signal specification for the SLK300 is not uniform across model years. The 2009 and 2011 model years use the 12496, while the 2010 model year uses the PY21W, making direct year-to-year interchangeability inadvisable without confirming the specific model year.
The PY21W follows the ECE standard used in Europe and internationally. It is a single-filament amber bulb rated at 12V and 21W, fitted with a BAU15s offset bayonet base. The offset pin configuration of the BAU15s base prevents incorrect installation of non-amber bulbs in the same socket.
The 12496 is a part number associated with Philips and Osram and is classified as a specialty halogen application bulb rated at 12V. Its designation as a specialty bulb indicates it is not a general-purpose replacement type and requires sourcing from compatible product lines.
The 3457NA and PY21W are not interchangeable. They differ in filament count, wattage, base type, and the standards body governing their specification, meaning a socket designed for one will not physically or electrically accept the other.
The dual-filament design of the 3457NA means it is capable of serving both a turn signal function and a secondary function such as parking or daytime running light within a single bulb housing, depending on the circuit configuration of the vehicle.