Nutrafin pH Wide Range Reagent Refill for Aquarium, 10ml Nutrafin ph wide range reagent refill is for use with the nutrafin ph wide range (4.5 - 9.0) test kit Ph levels should be monitored regularly as they have a direct effect on the well being and health of the fish Measures 1-inch length by 1-inch width by 3-inch height Comes in 10-milliliter refill pack