Hyosung GT250 Tail Light Bulb Size

The Hyosung GT250 tail light uses a P21/5W bulb size for illumination. The replacement chart covers 2007 to 2017 model years with corresponding bulb 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
2007-2017	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 Hyosung GT250 uses the P21/5W bulb type for its tail light across the 2007-2017 model years.
The P21/5W is a dual-filament bulb, meaning it contains two separate filaments within a single glass envelope, one rated at 21 watts and the other at 5 watts.
In a tail light application, the higher 21W filament typically serves the brake light function, while the lower 5W filament handles the running light function.
The P21/5W operates on a 12-volt electrical system, which is standard for motorcycles in this class.
This bulb type uses a BAY15d bayonet base, a two-pin offset base design. The offset pin placement is a deliberate anti-rotation feature that ensures the bulb is seated in only one orientation, keeping the filaments correctly positioned.
The P21/5W is governed by ECE (Economic Commission for Europe) standards and is recognized for use across European and worldwide markets, reflecting broad international availability.
Because the BAY15d base uses offset pins, it is not interchangeable with the similarly named BAY15s base, which is a single-filament bayonet type with symmetrically placed pins.