The Buick GS 400 uses an H5001 bulb size for high beam headlights and an H5006 bulb size for low beam headlights. The replacement chart covers 1968 to 1969 model 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 H5001 and H5006 are sealed beam units, meaning the lens, reflector, and filament are fused into a single glass assembly. When the filament fails, the entire unit requires replacement rather than an internal bulb swap.
The H5001 is a 4-inch square sealed beam unit operating at 12V, used in the Buick GS 400 as the high beam headlight for the 1968-1969 model years.
The H5006 is a 5.75-inch round sealed beam unit operating at 12V, serving as the low beam headlight across the same 1968-1969 model years.
Both the H5001 and H5006 conform to ANSI standards recognized in the United States and Canada, indicating standardized optical and electrical performance requirements for each unit type.
The H5001 and H5006 are physically distinct units. The square format of the H5001 and the round format of the H5006 make the two types non-interchangeable with each other.
Because both units are ANSI-standardized sealed beams, replacement units from any manufacturer conforming to the H5001 or H5006 specification are generally compatible with the corresponding socket position.