This is the rubber elbow behind the fuel filler cap. Over the years the rubber dries out and cracks and breaks and leads to a fuel leak, particularly when filling the tank. These are a simple 30min to 1 hour job to replace and will save you from potential engine fires, not to mention the expensive lost fuel.
Fits Baywindow VW Kombis from 1974 to 1979 fitted with an external filler cap. Will not fit 68 to 74 models that have a opening fuel door.