Penn Plax Airline Tubing for Aquariums &ndash;Clear and Flexible Resists Kinking, 25 Feet Standard Safe for salt and freshwater aquatic environments. Standard 3/16 inch diameter tubing is great for all your aquarium airline needs. Made from clear, flexible plastic. This airline tubing is built to last and withstand wear and tear. It is also resistant to kinking. Flexible plastic makes this tubing a breeze to work with. Great for use with aquarium ornaments or bubblers and many filters. Fits seamlessly in any home aquarium and virtually disappears in the water. Non-toxic so it will not harm your fish. You will not have to constantly replace old, broken tubing when you buy Penn Plax. It is ultra durable and will not become brittle or crack in time.