The Groz Internal Spring Caliper is designed for taking comparative measurements of the inner diameter and transferring the dimensions to a ruler. Manufactured from selected steel, these calipers have a spring joint for precise settings. The divider points hare hardened to 50-55 HRC for increased wear resistance.

The legs pivot on a roller and are tensioned by a bow spring, which allows for accurate adjustments up to as small as a micrometer. The fulcrum stud has a large bearing surface, which prevents side deflection of the legs, and the adjustment is made by opening and closing the legs using an adjusting nut.