The International S122 uses a 198 bulb size for both front and rear turn signal applications. The replacement chart covers 1956 to 1957 model 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 S122 uses the 198 bulb for both front and rear turn signals across the 1956-1957 model years.
The 198 is an ANSI-standardized bulb type, meaning its specifications are governed by a recognized North American standard applicable in both the United States and Canada.
The 198 bulb follows the T5 form factor, which refers to a tubular miniature wedge-base design with a tube width of 5/8 inch.
At 12 volts and 2 watts, the 198 bulb operates on a standard automotive electrical system voltage while drawing a very low wattage, consistent with small indicator lighting rather than high-output illumination.
The wedge base of the 198 bulb means it is held in its socket by the tension of the base itself, with no separate metal bayonet pins, which is a common trait of low-wattage miniature automotive bulbs.
The Light Duty designation applied to both model years indicates the S122 variant covered by these specifications falls within a lighter vehicle classification, which is relevant when cross-referencing fitment with other International truck lines that may share similar but distinct socket configurations.
Because the same 198 bulb size is specified for all four turn signal positions on the International S122, front and rear sockets share a common bulb type, though socket housing design may still differ between positions.