The Volvo V40 uses the 12961 bulb across all listed model years (2000-2003) for both front and rear side marker positions.
The 12961 is a Philips part number designating a miniature wedge bulb in the T10 form factor.
T10 refers to a tubular bulb with a nominal width of 10 units in the T-series classification system, commonly used in low-intensity automotive lighting applications such as side markers and courtesy lights.
The 12961 operates at 12 volts and 5 watts, which is consistent with standard automotive low-current signaling and marking circuits.
The base type for the 12961 is W2.1x9.5d, a wedge-style base that relies on wire contacts rather than a separate metal cap, allowing the bulb to be inserted directly into a compatible socket without rotation.
The W2.1x9.5d designation specifies the contact wire width and insertion depth of the wedge base, and substituting a bulb with a different base type would result in an incompatible fit even if the voltage and wattage ratings matched.
The front and rear side marker positions on the Volvo V40 share the same bulb specification across all listed years, meaning a single bulb type serves both locations on the vehicle.