Check the listing for details. JBJ C-Scope Refractometer Model CS/Manual For Testing Marine Salinity w/ Manual. Condition: Used. Listed at 19.99 USD. The JBJ C-Scope Refractometer Model CS is a handheld tool specifically designed for testing the salinity of marine water. It provides accurate readings to help aquarium enthusiasts and pet owners maintain the optimal water conditions for their aquatic pets. The manual included with this model ensures users can easily understand and use the device effectively, making it a convenient and reliable tool for monitoring and adjusting salt levels in marine environments.