Ensure your safety when swimming with this HTH 4 In 1 Test Kit Refills 3/4/5. It can be used to test the chlorine, bromine and pH levels in your pool. These refills will keep you supplied when your kit starts to run out. They are formulated for reliability and stability. These liquids are compatible with salt systems and can be applied directly to the pool for easy results. They are an ideal way to watch the chemical levels of your swimming pools.