Offset (or ET as it is often referred to) is the measurement taken from an imaginary line drawn through the centre of your wheel (as you look at it from the side), to the flat mounting surface that bolts to the vehicle’s hub. It is measured in millimetres. If the offset is higher the wheel will sit further into the car, away from the arch. If the offset is lower the wheel will sit further out, closer to the arch. Different vehicles require wheels with different offsets. For instance some cars require alloys with a low offset (around ET15) and others need wheels with a high offset (around ET50). It is normally the case that a small range of offsets will be suitable for the same car, for instance anywhere between ET35 and ET45 could be a good fitment for a particular vehicle. Our clever website makes sure that the wheels listed for your car or van have the right offset.