The Hino FFC1 uses the 1157 bulb across both its front and rear turn signal positions for the 1987-1988 model years.
The 1157 is an ANSI-standardized bulb type recognized across the United States and Canada, meaning it conforms to a defined set of electrical and physical parameters shared by compliant manufacturers.
It is a dual-filament bulb, which means it contains two separate filaments within a single envelope, each operating at a different wattage: 21W for the higher-intensity filament and 5W for the lower-intensity filament.
The bulb operates on a 12-volt electrical system, consistent with the standard automotive voltage found in light-duty and medium-duty vehicles.
The 1157 uses a BAY15d bayonet base, a two-pin offset base design that physically prevents incorrect single-filament substitutes from being seated in the socket, since the two pins are positioned at different heights.
Because the front and rear turn signal positions on the FFC1 share the same bulb type for both listed model years, a single replacement part covers all four turn signal sockets on the vehicle.
The dual-filament nature of the 1157 means the socket wiring must supply two separate circuits; substituting a single-filament bulb such as the 1156 would result in incomplete circuit function despite a similar physical appearance.