Valterra Blue Devil Cyanuric Acid Test B7519 is a 128 oz professional-grade solution designed to accurately measure cyanuric acid levels in pool and spa water. This test ensures proper water balance by helping maintain the correct stabilizer levels, which protect chlorine from rapid degradation due to UV exposure. Ideal for both residential and commercial pool maintenance, this reliable test solution provides clear and precise readings for optimal water quality management. The large 128 oz container allows for multiple tests, making it a cost-effective choice for regular pool care.