BMW X1 Brake Bulb Size

Additional Notes

• The P21W is the dominant bulb type across the BMW X1 brake light specifications, appearing in both the main brake light position across the 2012-2023 model years and the center high mount stop light position for the 2021 model year.
• The P21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base. The BA15s designation indicates a single-contact bayonet cap with a 15mm base width, which is a common format in European automotive lighting.
• The 2016-2019 model years of the BMW X1 carry an "Adaptive" designation alongside the P21W specification for the brake light position, indicating those vehicles are equipped with adaptive lighting systems that may affect how the bulb functions or is integrated within the assembly.
• The center high mount stop light on the 2022 BMW X1 uses the 12961 bulb, a Philips part number referencing a miniature wedge-type bulb with a W2.1x9.5d base, rated at 12V and 5W. This is a significantly lower wattage than the P21W used in the main brake light positions.
• The W2.1x9.5d base of the 12961 bulb is physically incompatible with the BA15s bayonet base of the P21W. These two bulb types are not interchangeable despite both operating on a 12V circuit.
• The center high mount stop light specification differs between the 2021 and 2022 model years. The 2021 model uses a P21W, while the 2022 model uses the 12961 wedge bulb, meaning the two consecutive years require different bulb types for the same position.