Suitable for high precision testing of straightness, checking on guides or scrapped surfaces or as reference, they have a shape studied to give maximum stability. The lapping on one face is carried out in three accuracy grades with tolerances as shown in the table below. They can be supplied with handles on the heads and with wooden case on request. Sides are ground (± 20 µm/m). Microplan® Test Report included. Calibration Certificate available on request*.