The Vespa PX 150 uses P21W bulbs for both front and rear turn signal applications, with this bulb size remaining consistent across the model line. The replacement chart covers vehicle production spanning 2005 to 2007.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is the sole bulb type specified for the Vespa PX 150 across all listed turn signal positions and model years.
The P21W operates at 12 volts with a 21-watt output, classifying it as a single-filament incandescent bulb intended for signalling functions such as turn indicators.
The P21W uses a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar width. The single-contact design reflects its single-filament construction, as opposed to the dual-contact BA15d base used on two-filament bulbs.
The P21W conforms to ECE (Economic Commission for Europe) standards, a regulatory framework recognized across Europe and numerous other markets worldwide.
The Vespa PX 150 uses the same P21W specification for both front and rear turn signals across the 2005-2007 model years covered in the specifications.
Because the front and rear turn signal positions share an identical bulb specification, a single P21W bulb type serves all four turn signal sockets on the vehicle.
The BA15s base is not interchangeable with the BA15d base despite the identical 15mm collar width, as the pin arrangement differs between the two fittings. Substituting a dual-contact bulb in a single-contact socket is not compatible.