The Elcometer 3230 Wet film Wheels, formally known as the Elcometer 120 consists of three circles. The central circle is of smaller diameter and is eccentric of the two outer circles. By rolling the gauge through a wet coating, the centre disc eventually touches the film. This point on the scale indicates the thickness.

If the volume to solids ratio of the coating is known, then the wet film thickness can be used to predict the dry film thickness.

Various measurement ranges are available from 0 to 25µm to 0 to 3000µm (0 to 1mil - 0 to 40mils) are available