General Hydroponics® pH Control Kit contains 8oz pH UP, 8oz pH DOWN, 1oz Test indicator and Vial. pH UP is a base solution formulated using potassium hydroxide and potassium carbonate. pH Down's acid formulation uses food grade phosphoric acid to lower the pH to the proper level. Widely recognized as a consistent and reliable product. The General Hydroponics® pH Test Indicator can help you maintain an ideal pH level (which is between 5.5 and 6.5). This can be achieved by monitoring your pH using the super concentrated drops found with the test indicator. Based on the test results, pH Up or pH down can be added to adjust the pH as needed. The General Hydroponics pH Test Indicator works across a wide pH spectrum (pH 4.0 – 8.5).