Mercedes-Benz B250e Turn Signal Bulb Size

The Mercedes-Benz B250e uses 3357NA and 3457NA bulbs for front turn signals, with 3357NA, 3457NA, PY21W, and 12496 bulb sizes specified for turn signal applications. The replacement chart covers 2016 to 2017 model years and documents bulb size specifications across the vehicle production range.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Front Turn Signal

Years	Bulb Size
2017	3357NA (With Halogen Capsule Headlamps)
2016	3457NA (With Halogen Capsule Headlamps)

Rear Turn Signal

Years	Bulb Size
2017	PY21W
2016	12496

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament wedge bulb (T25), natural amber glass. 12V, 27W.	3357NA
ANSI standard (US & Canada). Dual-filament wedge bulb (T25), natural amber glass. 12V, 27W/7W.	3457NA
ECE standard (Europe & worldwide). Single-filament amber bulb with BAU15s bayonet base. 12V, 21W.	PY21W
Philips/Osram part number. Halogen bulb, specialty application. 12V.	12496

Other Locations

Additional Notes

The 3357NA and 3457NA bulbs both follow the ANSI standard used in the United States and Canada, and both are T25 wedge-type bulbs rated at 12V. The key difference between them is filament count: the 3357NA carries a single filament at 27W, while the 3457NA carries dual filaments rated at 27W and 7W respectively.
The dual-filament design of the 3457NA means it serves two electrical circuits within a single housing, typically allowing one filament for turn signaling and a second for a secondary function such as parking or running light duty.
The Mercedes-Benz B250e uses the 3457NA in the front turn signal position for the 2016 model year, while the 2017 model year uses the 3357NA in the same position. These two bulbs are not interchangeable despite sharing the same T25 wedge base and identical 27W primary wattage, because the 3357NA lacks the second filament present in the 3457NA.
Both the 3357NA and 3457NA feature natural amber glass, meaning the color is produced by the glass envelope itself rather than by a coated or painted lens. The "NA" suffix in both part designations denotes this natural amber construction.
The rear turn signal specification shifts between ECE and proprietary part numbering across the two model years. The 2017 model year uses the PY21W, an ECE-standard bulb with a BAU15s bayonet base rated at 12V and 21W, while the 2016 model year uses the 12496, a Philips/Osram part number designating a specialty halogen application at 12V.
The BAU15s bayonet base on the PY21W is an offset single-contact base. The offset pin placement is a deliberate anti-misfit feature, preventing installation of non-amber bulbs sharing a similar base style into a socket designated for amber output.
The PY21W carries the ECE designation used across European and international markets, indicating it meets regulatory standards outside the ANSI framework that governs the 3357NA and 3457NA bulbs used in the front positions.
The 12496 designation originates from Philips and Osram part numbering conventions rather than from ANSI or ECE standardization, placing it in a category of bulbs identified by manufacturer catalog numbers rather than universal industry codes.
The front turn signal position on the Mercedes-Benz B250e specifies both the 2016 and 2017 fitments as applicable only with halogen capsule headlamps, indicating that vehicles equipped with a different headlamp technology may require a separate specification not reflected in these entries.