The BMW Z3 side marker requires a bulb size of 12961 for the lighting assembly. Data for the specific component covers the range from 1997 through 1998.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW Z3 uses the 12821 bulb across both front and rear side marker positions for the 1996-1998 model years.
The 12821 is a Philips part number designating a miniature wedge bulb in the T10 form factor, operating at 12 volts and rated at 5 watts.
The T10 designation refers to a tubular bulb with a nominal width of 10 millimeters, commonly found in low-intensity automotive lighting applications such as side markers and courtesy lights.
The W2.1x9.5d base type is a wedge-style connector, meaning the bulb is held in place by tension from the socket rather than by a bayonet or screw mechanism.
Because the same bulb size applies to all listed model years and to both the front and rear positions, a single bulb type serves all four side marker sockets on the Z3 across the 1996-1998 range.
The 5-watt output places the 12821 in the low-wattage category typical of marker and indicator lamps, which are not intended to produce driving illumination.
The W2.1x9.5d base specification is a standardized IEC designation, and any T10 wedge bulb sharing that base type is physically compatible with the same socket, though electrical ratings should match the original specification.