Innovative Viewing Systems Portal for Aquariums, 4-Inches The Portal allows you to enjoy the details of your fish, corals, and invertebrates like never before Magnetically attaches to your aquarium allowing you to move in any direction while staying securly i Specially developed prescription lenses magnify incredible details while the scrubbing pads on the i Made in the USA The Portal is a unique attractive addition to any aquarium. Designed for aquariums with a thickness between 7/16" and 5/8"