Super Pet CritterTrail Fun-nels Tee Tube - Assorted Colors Three-inch-long Tee Fun-nel Tube and Connector Ring is used to expand any CritterTrail habitat Easily connects to any CritterTrail habitat port and other Fun-nels tubes and accessories to expand your pet's living space Durable 3-inch-long plastic T tube snaps apart for easy cleaning, plus 2 connector rings for easy attachment to other CritterTrail parts Each tube has ventilation holes for your pet's safety 3-inch-long tube is 2.25 inches in diameter