The Mercedes-Benz SLK320 front turn signal requires 3457NA or 2357NA bulb sizes, while the rear turn signal uses 1156NA bulb size. The replacement chart covers 2001 to 2004 production 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 Mercedes-Benz SLK320 front turn signal uses two different bulb sizes across its model years: the 2357NA for 2001-2003 and the 3457NA for 2004.
The 3457NA is a dual-filament wedge bulb (T25) rated at 12V with a 27W high filament and 7W low filament, conforming to ANSI standards for the US and Canadian markets.
The 2357NA shares the same ANSI standard designation and also operates on a dual-filament design, rated at 12V with 26.9W and 8W filaments, but it uses a BAY15d bayonet base rather than a wedge-style fitting.
Because the 3457NA uses a wedge base and the 2357NA uses a BAY15d bayonet base, these two front turn signal bulbs are not physically interchangeable despite both being dual-filament types.
The rear turn signal on the SLK320 uses the 1156NA across all listed model years, 2001-2004, making it the only position with a consistent bulb specification throughout the entire production range covered.
The 1156NA is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base, and also conforms to ANSI standards for the US and Canadian markets.
The BA15s base of the 1156NA and the BAY15d base of the 2357NA are both bayonet-style fittings, but they differ structurally: BA15s has a single locating pin, while BAY15d has two offset pins, making them incompatible with each other.
All three bulb types across both turn signal positions feature natural amber glass, designated by the "NA" suffix, which produces the amber color through the glass itself rather than through a coated or painted lens.
The wattage difference between the two filaments on the 3457NA (27W and 7W) and the 2357NA (26.9W and 8W) reflects a typical automotive dual-filament configuration where the higher wattage filament serves the primary turn signal function and the lower wattage filament serves a secondary function such as parking or running light.