The SECO 25mm L-bar mini-prism is perfect for deformation or mining surveys, or in places where a fixed mounting is required. It's perfect for longer-range applications (up to approximately 2000 feet). The \L-bar" and prism housing are constructed of anodized aluminum. The mounting hole measures 10.30 mm (0.40 inches). The prism is permanently bonded to the holder, making it water and dust resistant. It features a -25mm offset.