The Spigot is located on the connector plate in the centre of the hub of the vehicle, which is the main load bearing connection that the alloy wheel sits on whilst aligning the studs and screwing back the wheel nuts. Generic aftermarket wheels have a larger Spigot hole connection than the spigot of the your vehicle, this is due to vehicles manufactures having different spigots sizes. So by increasing the Spigot size on the alloys the more vehicles the alloys will fit. The Spigot connection must be secure and firm against the wheel, so if the difference is to large spigot locating rings must be used. These are rings of hard plastic or metal that fit onto the cars spigot that allow for a snug connection and ensure the weight is firmly on the spigot and not the studs. It has been known that wheels can break connections under heavy manoeuvring or breaking if the wheel is not resting securely on the spigot.