Castroviejo Angled Caliper 0 to 20 mm Surgical Dental Medical Instruments 3.25" (8.3cm): Castroviejo Caliper is a measuring and marking instrument commonly used in procedures that involve muscles of the eye, or small bones and joints. This caliper is available with graduated 0-20mm markings and a screw lock that will lock the instrument in place when the measurement is obtained. The overall length of this caliper is 3-1/4 inches and tapers from the measurement end to the tip. The shanks and jaws are Angled.