The KTM 620 Duke uses H1 bulb size for both high beam and low beam headlight applications. The replacement chart covers 1994 to 1997 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The KTM 620 Duke uses the H1 bulb size for both high beam and low beam headlights across all listed model years, 1994-1997.
The H1 is a single-filament halogen bulb, meaning one filament handles one lighting function, which is why separate H1 units are required for the high beam and low beam positions rather than a single dual-function bulb.
H1 bulbs operate at 12 volts and 55 watts, placing them in the standard halogen output range for motorcycle headlight applications of that era.
The H1 uses a P14.5s base, a single-pin bayonet-style fitting that is specific to this bulb type and is not interchangeable with other common bases such as the P43t used in H4 bulbs.
The H1 is built to the ECE standard, which governs light output, beam pattern, and construction requirements across European and many worldwide markets, and the bulb also carries approval for use in the United States and Japan.
Because the 620 Duke uses identical H1 bulbs in both the high beam and low beam positions, the two sockets are not interchangeable in function despite accepting the same bulb type, as each socket is wired to a distinct circuit.