Aquarium Systems Saltwater Hydrometer is a durable, clear acrylic, swing-arm hydrometer that is easy to use and easy to read. Full-range results in both salinity and specific gravity (0 to 40 ppt salinity and 1.000 to 1.030 specific gravity) with color-blocked "safe zone" to make routine testing quick and accurate. Features large swing-arm pointer, extra-wide stable base and "easy-dip" design to keep your hands dry while obtaining water sample.