The Ducati ST4S uses H9 and H1 bulbs for high beam headlight functions, with H7 and H3 bulbs for low beam headlight functions, representing the specific size requirements for this motorcycle model. The replacement chart covers 2001 through 2004 vehicle production years and documents bulb size specifications across that period.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The H1 bulb is a single-contact halogen type operating on a straight filament design, rated at 55 watts with a P14.5s base. It served as the high beam headlight bulb in the Ducati ST4S across the 2001-2003 model years.
For the 2004 model year, the ST4S high beam headlight shifted to the H9 bulb, which uses the same PGJ19-5 base family as several other halogen types but operates at a higher wattage of 65 watts, producing greater luminous output than the H1 it replaced.
The H9 and H1 bulbs are not interchangeable despite both being single-filament halogen types. Their base configurations differ, meaning a 2004 high beam socket will not accept the H1 used in 2001-2003 models without modification.
The H3 bulb is a single-filament halogen type with a PK22s base and a distinctive two-pin connector rather than a twist-lock or push-in socket. It served as the low beam headlight bulb in the ST4S for the 2001-2003 model years.
For the 2004 model year, the ST4S low beam headlight uses the H7 bulb, a dual-contact halogen type with a PX26d base rated at 55 watts. The H7 is not compatible with H3 sockets due to the difference in base design.
The 2004 ST4S represents a distinct fitment category from the 2001-2003 models, requiring both a different high beam bulb (H9 instead of H1) and a different low beam bulb (H7 instead of H3), meaning replacement parts for the two groups are not interchangeable.