Sirona ™ test strips allow you to easily check your spa water for Sirona™ Simply Sanitizer levels, pH balance, total alkalinity, and calcium hardness. This pack includes 25 strips. To maintain a balanced spa environment, make sure your water falls within the recommended pH range of 7.2 to 7.8, total alkalinity of 80 to 120 ppm, and calcium hardness of 150 to 400 ppm. These test strips are specifically designed to work with Sirona™ Simply Sanitizer.