The Tropic Marin GH-Test makes it possible to quickly determine the total hardness of your aquarium water. This test kit will do approximately 100 tests (depending on test results) that are both fast and accurate. Tropic Marin test kits are the result of intensive research and development - directed at the needs of the serious aquarist. Extensive testing has been completed to assure accuracy and reliability. Tropic Marin tests are quick and easy to use. The kits contain glass vials, dosage syringes and recommendations to optimize the water quality.Tropic Marin GH Test+ measurement range: 1 - 20dH+ accuracy: 0.5/ 1dH+ for determining the total hardness in freshwater aquaria+ sufficient for approximately 100 applications+ reagent as refill pack separately available+ measured on the German hardness scale (dH)+ conversion Table for other units in the instruction manual included