Adapters are used to install wire wheels. The adapter is installed to a car with bolts or nuts and the wire wheel is then attached to the adapter with a spinner.
The thread of the adapter is different on the left and right sides of the car. This helps to prevent the loosening of the wheel during driving. The red adapter has a counter-clockwise thread and is installed to the right side of the car. The white adapter has a clockwise thread and is installed to the left side of the car.