BMW 850i front and rear side marker bulbs utilize 12961 and 12821 bulb sizes respectively, with each size corresponding to specific marker locations on the vehicle. The replacement chart covers 1993 to 1997 model years and details bulb size specifications across the production range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The BMW 850i uses the T10 miniature wedge form factor for both its front and rear side marker positions across the 1993-1997 model years.
The T10 designation refers to a tubular bulb approximately 10mm in width, commonly used in low-intensity automotive lighting applications such as side markers, courtesy lights, and instrument clusters.
The front side marker position on the 1993-1997 BMW 850i calls for bulb size 12961, a Philips part number rated at 12 volts and 5 watts.
The rear side marker position across the same model years calls for bulb size 12821, also a Philips part number rated at 12 volts and 5 watts.
Both the 12961 and 12821 share the W2.1x9.5d base type, which is the standard wedge base for T10 bulbs. The base code describes the contact width and pin spacing used to seat the bulb in its socket.
Despite sharing identical electrical ratings of 12V and 5W, and the same base type, the 12961 and 12821 carry distinct Philips part numbers, which indicates they are not confirmed as interchangeable by the specifications.
The 5-watt power draw of both bulb types places them in the low-consumption category typical of marker and position lighting, as opposed to higher-wattage bulbs used in headlamp or brake lamp applications.
The W2.1x9.5d wedge base is a tool-free, push-in fitment, meaning the bulb is retained by the socket housing rather than by a separate locking mechanism or bayonet twist.