The Lexus IS350 back up light utilizes a 921 bulb size for the lighting components. Data for the specific bulb requirements covers the range from 2006 to 2016.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 921 is an ANSI-standard wedge bulb in the T15 form factor, rated at 12 volts and 16 watts, and it is the bulb size specified for the back up light on the Lexus IS350 across the 2006-2009 and 2016 model years.
The T15 designation refers to the bulb's tubular shape, with the number indicating its width in eighths of an inch, and the wedge base means the bulb is held in place by the socket itself rather than by pins or a bayonet mechanism.
For the inner back up light, the 2006-2009 model years use the 3057 bulb rather than the 921, representing a different bulb type from the standard back up light on those same model years.
The 3057 is an ANSI-standard dual-filament wedge bulb in the T25 form factor, rated at 12 volts with a 27-watt high filament and a 7-watt low filament.
The dual-filament construction of the 3057 means it serves two distinct brightness levels within a single bulb, a characteristic that distinguishes it functionally from the single-filament 921.
The 921 and 3057 are not interchangeable despite both using wedge bases, as they differ in form factor, wattage, and filament count, and substituting one for the other would result in an incorrect fit or electrical mismatch.
The inner back up light on the 2017 IS350, specifically for production up to October 2016, uses the 921 bulb, aligning it with the same specification as the 2016 model year inner back up light.
Both the 921 and 3057 are rated under ANSI standards applicable to the United States and Canada, meaning they conform to a defined set of performance and dimensional criteria recognized across North American markets.