1STANDARD TOOL: This surveying prism has a effective diameter of 64mm and a offset of 0mm or 30mm, standard and practical. 2K9 GLASS: K9 optical glass lenses have been carefully polished, and a uniform and delicate coating on the surface can ensure the quality. 3ANTI WEAR: The prism is designed with ABS protective shell to ensure that the glass prism portion is anti wear, prolongs the service life. 4WIDE USAGE: This single tilt prism can be used together with a total station for land surveying and has a wide range of uses. 5MULTI PURPOSE: The total station surveying prism can be used for detection of tunnels, subways, mines, highways, etc. Item Type: Surveying Prism Material: K9 glass, ABS Effective Diameter: Approx. 64mm or 2.5in Constant: 0mm or -30mm Application: Detection of tunnels, subways, mines, highways, etc. Suitable for measuring instruments such as for Trimble Use: Widely used in various industries such as subways, railway, tunnel, dam, steep slope, etc. 1 x Surveying Prism 1 x Lid 1 x Storage Bag