The 4 in1 Test Strips are something everybody needs to help maintain their pool and spa. Each test strip will test the total bromine levels, the free chlorine amount, the pH levels as well as a total alkalinity. Its easy to use and will provide accurate results quickly. The total bromine test tells you the ideal level of total bromine needed to keep the water sparkling clean in spas and pools that use bromine as a sanitizer. The free chlorine test for pools and spas tells you if the chlorine levels are correct to regularly maintain a healthy swimming environment. The pH test ensures the water pH levels are correct to stop the water causing corrosion or scaling. Finally the total alkalinity is used to ensure a correct amount of alkaline is in the pool to stop sudden pH changes. Comes in a packet of 50 strips.