The MST 4.5mm Optical Zone Marker (Item #AR0250 4.50) is a purpose-built ophthalmic instrument in the Calipers, Gauges & Markers portfolio. Designed around its specific working geometry, it features 4.5mm diameter with cross hairs. Various marker diameters with cross hairs. Round handle. Overall length: 108mm. This combination of thoughtful design details and clearly defined specifications helps surgeons quickly identify the configuration that best fits their preferred technique and procedural needs.