The H7 is a single-filament halogen bulb operating at 12 volts and 55 watts, fitted with a PX26d base, which is a two-pin bayonet-style connector that locks into the headlight housing with a twist-and-lock mechanism.
The H7 bulb is standardized under ECE regulations, making it a globally recognized specification used across European and worldwide markets, with additional approval in the United States and Japan.
The Volvo S70 uses the H7 bulb size for both high beam and low beam headlights across the 1998-2000 model years.
Because the high beam and low beam positions share the same H7 specification, the bulb type is physically identical across both functions, though each position occupies a separate housing and socket.
The single-filament design of the H7 means each bulb serves only one lighting function, which is why separate bulbs are required for high and low beam operation rather than a dual-filament unit.
The PX26d base is not interchangeable with other common halogen bases such as H4 or H1, so substitution with physically similar-looking bulbs of a different base type would result in an incompatible fit.