Save money on a refractometer at Redwater NAPA. Keep track of the freezing point on your antifreeze with this handy tool. At 25% off, this UltraPro Refractometer is just $139.99. Measuring both propylene glycol and ethylene glycol, you can be sure your antifreeze is mixed correctly to do the job. The refractometer includes a calibration screwdriver and fluid dropper and comes in a durable nylon case.