The Geo Prizm brake light requires a 2057 bulb size for the specific lighting component located at the rear of the vehicle. Data for the bulb requirements covers the period from 1989 through 1997.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Geo Prizm uses the 2057 bulb for brake lighting across all model years in the specifications, covering 1989-1997.
The 2057 is a dual-filament bulb with a BAY15d bayonet base, operating at 12V with filament wattages of 26.9W and 8W for its high and low outputs respectively.
As a dual-filament design, the 2057 serves both brake and running light functions within a single housing, with the higher-wattage filament activating under braking.
The 2057 is noted as a brighter variant of the 1157, meaning the two share the same BAY15d base but are not identical in output, and substitution between them may affect brightness.
The center high mount stop light on the Geo Prizm uses one of two different bulb sizes depending on the model year, with 1989-1991 using the 1156 and 1993-1997 using the 921.
The 1156 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, making it incompatible with the dual-filament BAY15d socket used by the 2057 despite a superficially similar bayonet form.
The 921 is a wedge-style T15 bulb rated at 12V and 16W, which uses a fundamentally different base type than either the 1156 or the 2057, and the three bulb types are not interchangeable.
The shift from the 1156 to the 921 for the center high mount stop light between the 1991 and 1993 Geo Prizm reflects a socket change, meaning the physical base type in that position differs across those model years.
All three bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada.
The BAY15d base used by the 2057 features two pins offset at different heights, a design that prevents incorrect single-filament bulbs with the visually similar BA15s base from being seated in a dual-filament socket.