The Clorox Pool&Spa 3-Way Reagent Refills are meant to be used with the Clorox Pool&Spa 3-Way Test Kit. This swimming pool test kit works with the Clorox Pool app to test for pH and Chlorine or Bromine with simplified, color coded reagents for reliable poolside testing. Includes OTO, Phenol Red, and a water sample tube for accurate testing of pH and chlorine or bromine. Generally there are two types of test kits for swimming pools: liquid test kits and test strips. Some pool owners prefer test strips, since they provide information on factors such as calcium hardness, total alkalinity and stabilizer. Liquid test kits for pools such as this one are often preferred due to their simplicity and accuracy. Because they test the two most components of pool water (pH and Chlorine), liquid test kits give you the information you need to keep your pool balanced. Test your pool weekly using the Clorox Pool app for best results. Clorox Pool&Spa 3-Way Reagent Refills for Swimming Pool Water Testing: Swimming pool water 3-way testing kit Tests for pH, chlorine, and bromine Includes OTO, Phenol Red, and a water testing sample tube Easy to read color standards Reliable poolside testing Simplified testing with color coded reagents