Volkswagen Thing front and rear turn signal bulbs utilize a P21W size across both positions. The replacement chart covers 1973 to 1974 model years with corresponding bulb specifications.
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 listed across all turn signal positions for the Volkswagen Thing, covering both the front and rear turn signals for the 1973-1974 model years.
The P21W operates on a 12-volt electrical system and draws 21 watts, which is the standard wattage for single-filament automotive signalling applications under the ECE regulatory framework.
As a single-filament bulb, the P21W is dedicated to one lighting function per socket, meaning it does not serve a dual purpose such as combining turn signal and brake light operation within the same bulb.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base, consistent with its single-filament design.
The BA15s base is distinct from the BA15d base, which carries two contacts for dual-filament bulbs. Substituting a BA15d bulb in a BA15s socket is not mechanically compatible due to the differing contact configurations.
The P21W designation follows ECE (Economic Commission for Europe) standardization, meaning the bulb specification is defined by international regulatory standards rather than manufacturer-specific sizing conventions.
Because the same P21W specification applies to both the front and rear turn signal positions, the Volkswagen Thing uses a single bulb type across all four turn signal sockets, which simplifies parts interchangeability between positions on the vehicle.