Peugeot 505 front and rear side marker bulbs utilize a 12821 bulb size for both locations. Replacement chart data covers 1980 to 1985 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 Peugeot 505 uses the 12821 bulb across all listed model years (1980-1985) for both front and rear side marker positions.
The 12821 is a Philips part number designating a miniature wedge bulb in the T10 form factor, rated at 12 volts and 5 watts.
The T10 designation refers to the bulb's tubular envelope, with the number indicating a width of 10 millimeters expressed in eighths of an inch.
The base type is W2.1x9.5d, a wedge-style base in which the glass envelope itself acts as the retention mechanism rather than a separate metal base with pins.
The W2.1x9.5d base specification defines a contact width of 2.1mm and an insertion depth of 9.5mm, which determines socket compatibility.
Because the Peugeot 505 uses the same 12821 bulb in all four side marker positions, front and rear sockets accept the same replacement unit without substitution.
The 5-watt rating places the 12821 in the low-wattage category typical of marker and courtesy lighting, as opposed to the higher wattages associated with headlamp or stop lamp applications.
Wedge-base bulbs such as the T10 W2.1x9.5d are not interchangeable with bayonet-base or festoon-base bulbs, even when voltage and wattage ratings match.