Secure the screen lid to any terrarium or aquarium! Select the small size for terrariums and glass aquariums that hold 5 to 20 gallons. Use the large size to secure screen tops on 30 gallon or larger habitats. Fits most standard lids. Easily adjusts to fit any non-standard aquarium size. Use 2 clips per enclosure to ensure your pet is safe and protected. No escape artists will get out and no nosey cats will be getting in!