The Ducati ST3 headlight bulb specifications include an H9 size for high beam and H7 size for low beam applications. The replacement chart covers 2004 through 2007 model years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ducati ST3 uses the H9 bulb type for the high beam headlight across the 2004-2007 model years. The H9 is a halogen bulb operating at 65 watts with a PGJ19-5 base, designed for high-intensity forward projection.
The low beam headlight on the ST3 uses the H7 bulb type across the same 2004-2007 span. The H7 is a single-filament halogen bulb rated at 55 watts with a PX26d base, one of the most widely produced automotive halogen types.
The H9 and H7 bulbs share a similar physical form factor but are not interchangeable. Their bases differ, and installing an H9 in an H7 socket or vice versa is not possible without modification.
Although the H9 and H7 are both members of the H-series halogen family, the H9 operates at a higher wattage than the H7, which means the two positions draw different levels of electrical current from the motorcycle's charging system.
The fitment of H9 for high beam and H7 for low beam remained consistent across all four model years covered in the specifications, indicating no mid-cycle changes to the headlight bulb configuration on the ST3.
H7 bulbs are available from a wide range of manufacturers and are also used in many four-wheeled vehicles, which contributes to broad parts availability for the low beam position on the ST3.
The H9 bulb, while less common than the H7, is a direct-fit halogen type and is not a proprietary or vehicle-specific part. It is used across various motorcycle and automotive applications that require a higher-output high beam source.