White/GMC WHEB front side marker bulb size measures 1157, while rear side marker bulb size measures 194. The replacement chart covers 1991 to 1995 vehicle production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The White/GMC WHEB uses the 1157 bulb for the front side marker position across the 1991-1995 model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W filament configuration, conforming to ANSI standards recognized in both the US and Canada.
The dual-filament design of the 1157 means it carries two separate filaments within a single envelope, each operating at a different wattage, which is a defining characteristic that distinguishes it from single-filament alternatives.
The BAY15d bayonet base of the 1157 features offset pins, a physical trait that prevents incorrect installation of single-filament bayonet bulbs into the same socket.
The rear side marker position on the WHEB uses the 194 bulb across the 1991-1995 model years.
The 194 is a miniature wedge bulb of the T10 type, rated at 12V and 3.78W, also conforming to ANSI standards recognized in both the US and Canada.
The wedge base of the 194 relies on the bulb's own glass envelope and wire leads to make electrical contact, rather than a separate metal base, which is a structural distinction from the bayonet-style 1157.
The front and rear side marker positions on the WHEB require different bulb types, and the 1157 and 194 are not interchangeable due to differences in base type, wattage, and filament configuration.