Features GLASS MATERIAL: The prism lens uses excellent K9 glass assembly, which not only ensures accurate locating, but also has high durability. PRISM CYLINDER: This prism uses silver plated cylinder, protects prism with a diameter of 62mm, with an accuracy of less than 5 arcseconds. HIGH ACCURACY: The tilted target can be inverted and adjusted to an offset of 0, ‑30mm, and accompanying aiming sight improves accuracy. STANDARD SIZE: The circular prism lens has a standard size, easy to install and maintain, and equipped with a cover to provide good protection. WIDE APPLICATION: Widely used in subways, railways, tunnels, dams, steep slopes, mines, highways and other detection, with strong practicality. Specification: Item Type: Prism Lens Material: k9 Glass, ABS Effective Diameter: Approx. 64mm / 2.5in Constant: 0mm, -30mm Application: Widely used for testing tunnels, subways, mines, highways, dams, steep slopes, etc., suitable for measuring instruments. Package List:1 x Prism Lens 1 x Cover 1 x Storage Bag Package List 1 x Prism Lens 1 x Cover 1 x Storage Bag