This Refractometer tells you exactly the freeze protection of your coolant system (whether ethylene glycol or propylene glycol) and whether your battery requires a recharge or not. Gone forever are the inaccurate readings of the litmus paper tests and specific gravity floats. In fact, a Refractometer test is the only OEM-approved method for testing the freeze point of antifreeze/coolant. Simply place a drop of engine coolant or battery acid onto the prism, close the flap, and look at the large, easy-to-read scale through the adjustable viewfinder. No guessing, no more inaccurate readings. You'll know exactly the condition of your sample. So when the dealer says you need to replace that battery or your entire coolant system, you'll know if he's pulling your leg or not. The storage case includes cleaning fluid and dropper, screwdriver and cleaning cloth. This professional quality tool will pay for itself the first time you use it!