The BMW M3 brake light uses H21W, P21W, and P21/4W bulb sizes depending on the specific production period for the vehicle. Available data covers the range from 1988 through 2018 for the various components listed.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
Brake
If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.