Fun-nel Bubble plugs are the ideal way to close off openings in your CritterTrail habitat, accessories or Fun-nel Tubes while leaving a small viewing area for your pet. Easy to connect and pull apart so you can add space and more roaming area in minutes. Durable construction keeps your pets safe. Buy any of our wide assortment of Fun-nel tubes and accessories to create your own unique habitat for your pet. Bubble Plugs come in random assorted colors.