Kubota RTV400Ci Turn Signal Bulb Size

Kubota RTV400Ci rear turn signal bulb size is P21/5W. The replacement chart covers 2015 to 2018 vehicle production years with bulb specifications.

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

Rear Turn Signal

Years	Bulb Size
2015-2018	P21/5W

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

The P21/5W is the rear turn signal bulb used in the Kubota RTV400Ci across the 2015-2018 model years.
The P21/5W is a dual-filament bulb, meaning it contains two separate filaments within a single glass envelope, each rated at a different wattage.
The bulb operates on a 12-volt electrical system, with the two filaments rated at 21 watts and 5 watts respectively.
The higher 21-watt filament typically serves the turn signal or brake light function, while the lower 5-watt filament serves a secondary role such as a tail or parking light.
The P21/5W uses a BAY15d bayonet base, which is an offset twin-pin fitting designed to prevent incorrect installation by ensuring the bulb can only be seated in one orientation.
The P21/5W is governed by ECE standards, a regulatory framework recognized across Europe and numerous other markets worldwide.
Because the BAY15d base is offset, it is not interchangeable with the BA15d base, which shares a similar appearance but uses pins at equal heights rather than staggered ones.