1、SPECIFICATIONS: Circular reflector prism, 3 heads design, the effective diameter is 64mm, the measuring prism offset is 0/‑30mm. 2、OPTICAL GLASS LENS: The prism lens is made of excellent optical glass with fine polishing, and the delicate coating can ensure long term use. 3、STABLE STAND: The surveying prism is equipped with a stable stand, convenient to install the prism on the total station for use. 4、ABS HOUSING: The prism housing is made of excellent ABS, which is impact resistant, aging resistant, and has a long service life. 5、WIDE APPLICATION: The 3 head prism is widely used for tunnel, railway, dams, mines, highway detection, which is compact and practical. Item Type: Prism Material: Optical Glass, ABS Effective Diameter: Approx. 64mm / 2.5in Constant: 0mm/-30mm Use: Widely used in subway, railway, tunnel, dam, steep slope, mine, highway, and other detection. 1 x Prism 3 x Covers 1 x Storage Bag