This DD Seawater Refractometer is a must-have for any marine aquarium enthusiast. It allows you to quickly and easily test the water refractivity of your fish tank, making it an essential tool for maintaining a healthy and vibrant marine ecosystem. With its precision engineering and durable construction, this refractometer is built to last and will provide reliable and accurate readings for years to come. The unit is made in the United States and comes with all the necessary accessories for easy use. It is perfect for both beginners and experienced fish keepers, and is sure to become an indispensable part of your aquarium management routine. So why wait? Get your hands on this top-quality DD Seawater Refractometer today and start enjoying a healthier, more beautiful marine ecosystem in your fish tank!