Check sanitizer level, calcium hardness, alkalinity, and pH with one easy-to-read test strip. Keeping your water balanced is now easier than ever. It includes an easy-to-read chart to help tell if your spa water is within the proper ranges. These strips are compatible with chlorine and ozone sanitizers that are used in hot tub and spa systems. These strips are incredibly easy to use, simply immerse the test strip for 2 seconds, remove with the pads facing up, shake once to remove any excess water, and read immediately. It features a patented PopTop lid that protects strips from moisture and UV light. Compatible with leisure time free sanitizing system, biguanide spas, and hot tubs.