This 8 Inch cylindrical viewer acts like a scuba mask to reduce surface distortion so you can better view corals and other items in your tank. The large viewing surface is ideal for taking photos inside your aquarium. It allows a clearer view of your corals from above, and because it floats on the surface of water, you don’t have to hold it in place when you snap photos of your corals. It is also helpful for a variety of other aquarium tasks that require a closer look, such as routine maintenance, aquascaping, or coral propagation. They are really easy to use and are really convenient.