Triumph Daytona 1200 Tail Light Bulb Size

The Triumph Daytona 1200 tail light uses a P21/5W bulb size for illumination. The replacement chart covers vehicle production spanning 1993 to 1997.

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
1993-1997	P21/5W

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

The Triumph Daytona 1200 uses the P21/5W bulb for its tail light across the 1993-1997 model years.
The P21/5W is a dual-filament bulb, meaning it contains two separate filaments within a single glass envelope. The 21W filament serves the brighter stop or turn signal function, while the 5W filament handles the lower-intensity running light function.
The P21/5W operates on a 12V electrical system, which is standard for motorcycles of this type.
The bulb 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 the bulb from being inserted in the wrong orientation, ensuring each filament connects to its correct circuit.
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 uses offset pins, it is not interchangeable with the BA15d base, which carries pins at equal heights. Substituting a BA15d bulb in a BAY15d socket would result in incorrect filament-to-circuit alignment.