The Peugeot 304 front and rear side marker bulb size is 12821, a standardized bulb specification for this model. The replacement chart covers 1971-1972 production years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Peugeot 304 uses the 12821 bulb across both its front and rear side marker positions for the 1971-1972 model years.
The 12821 is a Philips part number designating a miniature wedge bulb in the T10 form factor, operating at 12 volts and rated at 5 watts.
The T10 designation refers to a tubular bulb with a nominal width of 10 millimeters, a common sizing standard in low-wattage automotive lighting applications.
The 12821 uses a W2.1x9.5d base, which is the standard wedge-type base for T10 bulbs. The "W" prefix indicates a wedge configuration, meaning the base of the glass envelope itself acts as the retention mechanism rather than a separate metal cap.
Because the same bulb number applies to both the front and rear side marker positions across both listed model years, the 304 requires no differentiation between front and rear replacements for this function.
The W2.1x9.5d base is not universally interchangeable with all T10-sized bulbs, as some T10 variants use different base configurations. Fitment depends on matching both the physical base type and the voltage and wattage ratings to the original specification.