The Alfa Romeo 164 brake light utilizes a P21W bulb size for the rear lighting system. Data for the specific component covers the range from 1991 to 1995.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Alfa Romeo 164 uses the P21W bulb for the brake lights across the 1991-1995 model years.
The P21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The 1156 bulb is specified for the center high mount stop light on the Alfa Romeo 164 across the same 1991-1995 model year range.
The 1156 is an ANSI-standard single-filament bulb rated at 12V and 21W, also fitted with a BA15s bayonet base.
The P21W and the 1156 share identical electrical ratings and the same BA15s bayonet base type, with the primary distinction being their regional standards: ECE for the P21W and ANSI for the 1156.
Because both bulbs carry the same base type and wattage, physical fitment between the two is mechanically possible, though each designation reflects a different regional certification standard.