Features Using Good Glass: Having been through excellent workmanship, the optical glass comes with high accuracy to largely improve the measurement. Clear Reflection: Designed to have ‑17mm constant and 25.4mm effective diameter, the mini surveying prism ensures clear image in reflection. Great Durability: The lens is fully covered by sturdy ABS plastic housing, which has great durability against wearing and long term use. Easy Installation: The clear thread inside the brass adapter blow enables the prism to easily connect to 5/8in x 11 threaded rod or tripod. Wider in Utility: Suits for Trimble and other measuring instrument, the prism can be used on the testing of tunnels, subways, mines, etc. Specification: Item Type: Total Station Prism Material: ABS Glass Diameter: Approx. 25.4mm / 1in Prism Constant: -17mm Application: For the testing of tunnels, subways, mines, highways, etc. Suitable for measuring instruments such as for Trimble. Usage: Widely used in various industries such as subways, railways, tunnels, dams, steep slopes, etc.  Package List:1 x Total Station Prism Package List 1 x Total Station Prism