Contains one (1) API REPLACEMENT TEST TUBES WITH CAPS For Any Aquarium Test Kit Including API Freshwater Master Test Kit 24-Count Box Compatible with any aquarium water test kits including freshwater and saltwater test kit, pH test kit, ammonia test kit, nitrate test kit, reef test kit, calcium test kit and more The API test tubes are perfect to replace API Freshwater Master Test Kit tubes, API Saltwater Master Test Kit tubes, API Reef Master Test Kit tubes, API Pond Master Test Kit tubes and any other API Test Kit tubes Snap-tight plastic caps Use when original tubes have been lost or damaged