Offset is the distance between the centerline of the wheel and the plane of the hub (mounting surface of the wheel). It can be either positive or negative, and is usually measured in millimeters. Sometimes you might have seen a German prefix “ET” meaning “Einpresstiefe” or, literally, “insertion depth” is used to refer to offset. In some cases, “-” negative sign or “+” positive sign is used in front of offset number.
