Upgrade 7 IN 1 TestsCan simultaneously test 7 kinds of total hardness, total chlorine, bromine, free chlorine, PH, cyanuric acid (stabilizer) and total alkalinity. More effective than other spa test strips. Water quality should be tested at least every week, and more frequently under heavy usage. At Home Test StripsThe spa hot tub water test strips set have instant and reliable results, simple and clear instructions. Just dip and compare to the big color chart on the bottle. The desired range is marked on the bottle. 17S Fast & AccurateImmerse the pool test strip in water for 2 seconds and let it keep in the air for about 15 seconds, then match the color of the test strip to the back of the bottle to get a reading. it only takes 17 seconds. Pool test strips are easy to use even for beginners High-Percision ResultsDesigned for warm water, these water hardness test strips easily provide instant and reliable results without much effort. Come with an excellent color card to explain the test results meaning, also tell you which aspects you should take care of about your pool. Pool & Spa EssentialsHot tub test strips suitable for drinking water, aquariums, swimming pools and spas, sewage and other liquids. Using Test strips, you can make sure you keep the right amount of chemicals in your pool to avoid health problems and equipment damage.