Evans Hand Held Refractometer is designed to accurately test for residual water content after installing Evans Waterless Coolant products. The elimination of water allows Evans Waterless Coolant to work at peak performance. Simply take a sample of fluid after there has been thorough circulation of the coolant through all parts of the cooling system, including the radiator and the heater core. Your goal is to keep the water content below 54.4 Brix (3% water). Included with the Refractometer are a soft storage case, pipette for dripping test fluids, a mini screwdriver for scale calibration and a detailed user guide.