International L121 uses 194 bulb size for front side marker and 97 bulb size for rear side marker applications. The replacement chart covers 1950 to 1952 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 International L121 uses the 194 bulb for the front side marker position across the 1950-1952 model years, and the 97 bulb for the rear side marker position across the same span.
The 194 is an ANSI-standardized miniature wedge bulb of the T10 type, rated at 12 volts and 3.78 watts. Its wedge base design means it requires no separate metal base, as the glass envelope itself acts as the retention mechanism within the socket.
The 97 is an ANSI-standardized single-filament bulb rated at 12 volts and 13 watts. It uses a BA15s bayonet base, which features a single locating pin on the side of the base for insertion and twist-lock retention.
The 97 bulb is noted as a variant of the 1156. While the two share a BA15s bayonet base, they are not interchangeable in all applications, as they differ in wattage and filament position, which can affect fit and function in housings designed for one or the other.
Both the 194 and 97 carry ANSI standardization applicable to the United States and Canada, meaning their electrical and physical specifications conform to a defined industry standard within those markets.
The wattage difference between the two bulbs is substantial. The rear-mounted 97 at 13 watts draws considerably more power than the front-mounted 194 at 3.78 watts, reflecting the differing visibility requirements typically associated with rear versus front side marker functions.
Both bulb types operate on a 12-volt electrical system, consistent with the standard automotive voltage architecture of the era in which the International L121 was produced.