Mercedes-Benz CLA250 front and rear turn signal bulbs use PY21W or 12496 size replacements. Data spans 2014 to 2020 model years with bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz CLA250 front turn signal specifications reference three distinct bulb types across the 2014-2020 model years: PY21W, 12496, and 3457NA, with a single instance of the 3357NA in 2016.
The PY21W is an ECE-standard single-filament amber bulb rated at 12V and 21W, fitted with a BAU15s bayonet base. This base type is offset, meaning it is not interchangeable with the more common BA15s straight-pin bayonet base used in many other automotive applications.
The 3457NA and 3357NA are both ANSI-standard T25 wedge bulbs with natural amber glass, but they differ in filament count. The 3457NA is dual-filament at 27W/7W, while the 3357NA is single-filament at 27W. These two types are not functionally interchangeable despite their physical similarity.
The 12496 is a Philips/Osram part number designation for a 12V halogen bulb intended for specialty applications. Its use across both front and rear turn signal positions on the CLA250 reflects its role as a manufacturer-specified fitment rather than a general-purpose replacement type.
The front turn signal for the 2020 CLA250 specifies the PY21W without any headlamp qualifier, while all earlier model years from 2014-2019 carry a "With Halogen Capsule Headlamps" condition, indicating a headlamp-dependent fitment distinction in those years.
The rear turn signal for the 2020 CLA250 also carries no headlamp qualifier, whereas the 2014-2019 rear turn signal entries all specify "With Halogen Capsule Headlamps," consistent with the pattern seen on the front position.
The front turn signal position shows a bulb change between the 2019 and 2020 model years on the CLA250, shifting from the 12496 to the PY21W. These two bulb types differ in base design and wattage, making them non-interchangeable.
The rear turn signal for the 2017 CLA250 specifies the PY21W, while the surrounding model years (2016 and 2018) specify the 12496. The PY21W and 12496 use different base types and are not interchangeable, making year-specific verification necessary for that position.
The 3457NA and 3357NA bulbs specified for the front turn signal position carry the "NA" suffix, which denotes natural amber glass coloring. This amber tint is built into the glass envelope rather than applied as a coating, which affects light output characteristics compared to clear-glass equivalents.
The front turn signal of the 2016 CLA250 is the only instance in the specifications where the 3357NA single-filament bulb appears, while the surrounding years (2014-2015 and 2017-2018) specify the dual-filament 3457NA. Substituting one for the other in that position would result in a functional mismatch.