Polaris Sport Touring Brake Bulb Size

Additional Notes

• The 921 bulb is a single-filament wedge type (T15) operating at 12V with a 16W output, conforming to ANSI standards for the US and Canadian markets. Its single-filament design means it produces one fixed light output level, without a separate lower-intensity mode.
• The 1157 bulb is a dual-filament type fitted with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively. The BAY15d base uses two offset pins to ensure correct orientation during installation, preventing the filaments from being reversed.
• The 3157 is a dual-filament wedge bulb (T25) rated at 12V with filaments drawing 27W and 7W. Unlike the 1157, it uses a wedge base rather than a bayonet fitting, making the two bulbs physically incompatible with each other's sockets despite both being dual-filament types.
• The Polaris Sport Touring used the 921 bulb for the brake light across the 1995-1999 model years, the 1157 across the 2000-2003 model years, and the 3157 for the 2004 model year. Each of these three bulb types has a distinct base configuration, meaning none of them are interchangeable with one another.
• The transition from the 921 single-filament bulb to the dual-filament 1157 in the 2000 model year represents a change in brake light circuit design, as dual-filament bulbs serve two separate electrical functions within a single housing, typically a running light function and a brighter brake signal.
• All three bulb types listed in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating a standardized electrical and photometric classification shared across North American markets.
• The 3157 (T25) and 921 (T15) are both wedge-base bulbs, but their differing body sizes and filament counts make them non-interchangeable. The T25 designation of the 3157 indicates a larger bulb body than the T15 of the 921.