Hub extenders are used to make a dramatic change to the track width of a vehicle. These mate to the existing hub like a spacer would, only they are then bolted down using the original lug holes and a completely new set of lugs embedded in the extender provide a solid hold to the wheel. When installed they relocate the hub mounting surface further outboard and can sometimes eliminate the need for custom hubs and longer suspension components. If you've installed a widebody kit or over-fenders these may well be your next purchase.
