Mercedes-Benz Sprinter Brake Bulb Size

Additional Notes

• The Mercedes-Benz Sprinter uses two distinct brake bulb types across its model years: the single-filament P21W and the dual-filament P21/5W.
• The P21/5W is a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament, mounted on a BAY15d bayonet base. The two filaments serve separate functions within the same housing, which is typical in combined brake and tail light circuits.
• The P21W is a single-filament bulb rated at 12V and 21W, using a BA15s bayonet base. It carries only one filament, meaning it serves a single lighting function rather than a combined one.
• Both bulb types follow the ECE standard, which is recognized across Europe and internationally, indicating they conform to a regulated performance and safety specification.
• The BA15s base of the P21W and the BAY15d base of the P21/5W are physically different. The BAY15d base has offset pins to prevent incorrect installation, while the BA15s base has symmetrical pins. These two bases are not interchangeable.
• The Sprinter used the P21/5W across the 2010-2020 model years, with the 2019-2021 entries noting a conditional fitment tied to halogen headlamp configuration.
• For the 2019-2021 Mercedes-Benz Sprinter, the P21/5W fitment is specified only for vehicles equipped with halogen headlamps, indicating that headlamp type influences brake bulb selection in those years.
• Starting with the 2022 model year, the Sprinter shifted to the P21W, a single-filament bulb, continuing through the 2025 model year.
• Because the P21W and P21/5W share a similar wattage rating on their primary filament but differ in base type and filament count, substituting one for the other is not a compatible swap.