These plastic parts are tightened into the body and serve as threads for the parker screws with which the air intake grilles are attached at the rear.
Plastic hardens over the years and as long as you don't touch it, it's fine. But if you want to disassemble a spreader nut, the parts usually break. With a good restoration, you will still have to take them apart to apply a new coat of paint to the bodywork instead of the spacer nuts and you will hardly be able to put new ones on.
Useful information from Paruzzi magazine and from our YouTube channel :
Se etter flere tekniske artikler på siden Paruzzi Magasinet