Suzuki Motorcycle GW250 Tail Light Bulb Size

Additional Notes

• The P21/5W is the tail light bulb type specified for the Suzuki Motorcycle GW250 across the 2013-2017 model years.
• P21/5W is an ECE-standard dual-filament bulb, meaning it contains two separate filaments within a single glass envelope. The higher 21W filament serves the brake light function, while the lower 5W filament handles the running light function.
• The bulb operates on a 12V electrical system, which is standard for motorcycles in this class.
• The P21/5W uses a BAY15d bayonet base. The BAY15d designation indicates an offset pin configuration, where the two retaining pins are positioned at different heights on the base. This offset prevents incorrect installation of a single-filament bulb in place of the dual-filament unit.
• The ECE designation on the P21/5W indicates the bulb conforms to United Nations Economic Commission for Europe regulations, a standard recognized across Europe and numerous other markets worldwide.
• Because the BAY15d base is physically keyed by its offset pins, a single-filament BA15s bulb cannot be substituted without risking incorrect circuit behavior, even if it fits partially into the socket.