Ferrari 348 GTS front turn signal bulbs measure P21W in size while rear turn signal bulbs measure 1156 in size. The replacement chart covers 1993 to 1994 production years and contains bulb size specifications for turn signal applications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ferrari 348 GTS uses two distinct bulb standards across its front and rear turn signal positions for the 1993-1994 model years.
The front turn signal on the 348 GTS calls for the P21W bulb, which follows the ECE standard used in Europe and worldwide markets.
The rear turn signal position uses the 1156 bulb, which follows the ANSI standard applied in the US and Canadian markets.
Despite carrying different part designations, the P21W and 1156 share identical electrical ratings of 12 volts and 21 watts, as well as the same BA15s bayonet base configuration.
The BA15s base is a single-contact bayonet fitting, meaning the bulb is secured by two small pins on the base and makes electrical contact through a single point at the bottom.
Both the P21W and 1156 are single-filament bulbs, a construction suited to dedicated signalling functions that require only one light output state.
Because the P21W and 1156 share the same base type and wattage, physical fitment in the socket may be possible in either position, though the differing certification standards reflect regional regulatory distinctions rather than purely electrical ones.
The consistent use of P21W at the front and 1156 at the rear across both the 1993 and 1994 model years indicates no change in bulb specification during that production period.