Subaru Crosstrek Back Up Light Bulb Size

Additional Notes

• The 7440 bulb is the most frequently specified backup light for the Subaru Crosstrek, covering the 2018-2023 model years across six consecutive years.
• The 7440 is a single-filament T20 wedge bulb rated at 12V and 21W, conforming to ANSI standards for the US and Canadian markets.
• The 2024 Subaru Crosstrek requires a 1157 bulb, which differs fundamentally from the 7440 used in prior years. The 1157 uses a BAY15d bayonet base rather than a wedge-style fit, making the two bulbs physically incompatible with each other.
• The 1157 is a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament, whereas the 7440 carries only a single filament at 21W.
• The 2017 Crosstrek uses a 921 bulb, a T15 wedge type rated at 12V and 16W. Although the 921 shares the same wedge-style base as the 7440, its lower wattage and smaller T15 housing distinguish it from the T20 form of the 7440.
• The 921 and 7440 are both wedge-base bulbs, but their differing physical sizes mean they are not interchangeable without risk of an improper fit in the socket.
• All three bulb types listed in the specifications, the 1157, 7440, and 921, operate on a 12V electrical system and comply with ANSI standards applicable in both the United States and Canada.
• The shift from the 921 in 2017 to the 7440 in 2018 represents a change in both wattage output and bulb housing size for the backup light position.