Easy to use. See back panel. Trusted quality since 1927. Quick check concentration levels. Inspect for rust and sediment. Works with all ethylene glycol coolants. Tests freeze-up protection. Test when engine is cool; Pointer must be totally immersed fluid should be level with horizontal line at top of tester. Tap to dislodge air bubbles. Freeze point. (-34 degrees F) 50 % concentration recommended (-37 degrees C). Easy test for winter freezing and summer boil over protection. Regular monitoring can help keep you vehicle running. Recommended for use with Prestone and Prestone Dex-Cool antifreeze/coolant and all other ethylene glycol coolants. Boil over protection. 15 lb. Cap (103 kpa). (265 F) 50% Conc. Recommended (129 degrees C). www.prestone.com. Watch how to do it yourself. Visit www.prestone.com. Questions? Call 800-890-2075. Made in Taiwan.