A4 Lug Nuts are an essential component for the wheels of your car. Most cars either have 4 or 5 A4 Lug Nuts and these nuts are used to fasten the wheels of your car to the axel of your car. A4 Lug Nuts can be made of a multitude of materials and can come in a variety of colors, styles and finishes to match your wheels. Some A4 Lug Nuts have special 'keys' to attach to the wrench you use to remove the wheels. This is designed to prevent theft of the wheels.