Major Improvements of Sokkia's LDT520 Laser Digital Theodolite, A 600-meter laser range, the World's longest laser range as of October 2008, Dust and water protection of IP66; the top of its class, Equipped with the market-proven advanced encoders for the highest reliability and lower power consumption, Longer battery life, Operable in tighter spaces, Emits both focused and parallel beams. Tangent locks keep you on line all day.