BMW 550i Back Up Light Bulb Size

Additional Notes

• The BMW 550i uses the 921 bulb size for the back up light across all listed model years, spanning 2006-2016.
• The 921 is a wedge-type bulb, classified under the T15 designation, which refers to its tubular glass envelope measuring 15/8 inches in length.
• Wedge bulbs use a plastic base with no separate metal pins, relying instead on the base itself to make electrical contact within the socket.
• The 921 operates at 12 volts and draws 16 watts, which is consistent with standard automotive low-voltage electrical systems.
• The 921 bulb follows ANSI standards recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical specifications shared across those markets.
• The single bulb size across the entire 2006-2016 production span of the BMW 550i indicates a consistent socket type throughout that generation range.
• The T15 wedge form factor is a common fitment in reverse light applications across many vehicle makes, though interchangeability with other vehicles should be confirmed against their specific socket and wattage requirements before substitution.