The Eclipse Professional are hand-held optical refractometers that are primarily used for on the spot determination of Refractive Index of fluids or the concentration of solutions. They are incorporated with numerous scales and can be utilized in a number of operations in various industrial fields. The devices are available in a soft carrying case and is constructed with a push-on prism flap. These optical refractometers are characterized by their innovative sample 'dribble' option as well as their roll-proof supports.