15 centimeters (6 inches) from the bottom of the water to avoid the error caused by the oil film on the water. Keeping your hands clean and can prevent pollution of water from the fish pond. It is easy to read and the precision can be + (-) 0.001 units of specific gravity. Professional design make it able to get accurate reading when the temperature of the fishpond is at -28 degrees. , both inside and outside the cylinder can be read. The hydrometer that can float on the surface of the water is simple and easy to read. The proportion of water sample can be automatically detected. The proportion, and conductivity of sea water are shown once. Feature - ColorWhite - Material: Plastic - Size: 19x7.5x1.5cm. - 15 centimeters (6 inches) from the bottom of the water to avoid the error caused by the oil film on the water. - Keeping your hands clean and can prevent pollution of water from the fish pond. - It is easy to read and the precision can be + (-) 0.001 units of specific gravity. Professional design make it able to get accurate reading when the temperature of the fishpond is at -28 degrees. - , both inside and outside the cylinder can be read. The hydrometer that can float on the surface of the water is simple and easy to read. - The proportion of water sample can be automatically detected. The proportion, and conductivity of sea water are shown once. Package list: 1 x gravimeter