Offset (ET) is indicated in millimetres.
The parameter shows the distance between the rim centre axle and the wheel hub mounting surface.
A different offset affects the displacement of the rim in the wheel arch. It is important to know that the position of the rim in the wheel arch is not only dependent on the offset but also on the overall width of the rim.
For example, the 18″ x 8J ET45 rim protrudes out from the wheel arch almost as much as the 18″ x 7J ET35 rim.