The Ducati ST2 headlight bulb specifications include an H1 size for high beam and H3 size for low beam applications. The replacement chart covers 1997 to 2003 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 ST2 uses the H1 bulb for the high beam headlight across all model years from 1997-2003. The H1 is a single-filament halogen bulb with a P14.5s base, rated at 55 watts and operating at 12 volts.
The low beam headlight on the Ducati ST2 uses the H3 bulb across all model years from 1997-2003. The H3 is also a single-filament halogen bulb, but it uses a PK22s base, which is a push-and-twist style connector distinct from the P14.5s base found on the H1.
Because the H1 and H3 bulbs use different base types, they are not interchangeable with each other. Installing the wrong bulb type in either headlight position is not possible without modification, as the connectors and housings are physically incompatible.
Both the H1 and H3 are single-filament bulbs, meaning each serves only one lighting function. This is why the ST2 requires separate bulbs for high and low beam operation rather than a dual-filament bulb such as the H4.
The H1 bulb has a straight, single-ended design with the filament positioned along the bulb's central axis, which suits optical systems requiring precise filament placement for focused beam projection.
The H3 bulb features a compact form factor with a wire lead attached to the base rather than a pin-style connector, making it well suited for tight or angled headlight housing configurations.
The consistent use of H1 and H3 bulbs across the entire 1997-2003 production run of the ST2 indicates that the headlight housing design remained unchanged throughout the model's production life.