The White/GMC WG front side marker bulb uses a 1157 size, while the rear side marker bulb uses a 194 size. The replacement chart covers 1990 to 1995 model years with bulb size specifications for side marker applications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The White/GMC WG uses the 1157 bulb for the front side marker position across the 1990-1995 model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W filament configuration, and conforms to ANSI standards recognized in both the United States 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 characteristic relevant to fitment compatibility.
The rear side marker position on the WG uses the 194 bulb across the same 1990-1995 model years.
The 194 is a single-filament miniature wedge bulb of the T10 type, rated at 12V and 3.78W, also conforming to ANSI standards for the United States and Canada.
The wedge base of the 194 differs fundamentally from the BAY15d bayonet base of the 1157, making the two bulb types non-interchangeable between the front and rear side marker positions.
The 1157 and 194 are both ANSI-standardized types, meaning physical and electrical specifications are consistent across manufacturers producing bulbs under those designations.
The significant wattage difference between the 1157 front marker bulb and the 194 rear marker bulb reflects the distinct functional roles of each position on the vehicle.