The BMW L7 brake light requires a P21W bulb size for proper installation and function within the lighting assembly. Data for the specified component covers the range from 1986 to 1987.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is an ECE-standard single-filament signalling bulb rated at 12 volts and 21 watts, fitted with a BA15s bayonet base. The ECE designation indicates it meets European and internationally recognized lighting regulations.
The BA15s bayonet base uses a single contact at the base, which is a defining characteristic of the P21W. This distinguishes it from the BA15d base, which carries two contacts and is not interchangeable with BA15s sockets.
The BMW L7 uses the P21W for both the standard brake light and the center high mount stop light across the 1986-1987 model years.
The use of a single-filament bulb in the brake light position means the P21W serves a dedicated stop light function only, without a secondary filament for combined tail and stop light operation.
Because both the brake light and the center high mount stop light on the BMW L7 share the same P21W specification, the same bulb type is applicable to both positions without substitution differences.