Suzuki Motorcycle LT-F400F KingQuad FS/FSi Tail Light Bulb Size

Suzuki Motorcycle LT-F400F KingQuad FS/FSi tail light bulb uses a P21/5W size. The replacement chart covers 2008 to 2019 production years with corresponding bulb size specifications.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2008-2019	P21/5W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Dual-filament signalling bulb with BAY15d bayonet base. 12V, 21W/5W.	P21/5W

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Additional Notes

The Suzuki LT-F400F KingQuad FS/FSi uses the P21/5W bulb for its tail light across the 2008-2019 model years.
The P21/5W is a 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 P21/5W operates on a 12V electrical system, which is standard for most powersport and automotive applications.
This bulb type uses a BAY15d bayonet base. The BAY15d designation indicates an offset pin configuration, where the two pins are positioned at different heights on the base. This offset prevents incorrect installation, as a bulb with symmetrical pins cannot be seated in a BAY15d socket.
The P21/5W conforms to ECE (Economic Commission for Europe) standards, a regulatory framework recognized across Europe and numerous other markets worldwide.
Because the BAY15d base is an offset twin-pin design, it is not interchangeable with the BA15d base, which shares the same pin spacing but uses pins at equal heights. Substituting a BA15d bulb in a BAY15d socket is not possible without modification.