Kaytee CritterTrail Loop-D-Loop Accessory KitCritterTrail accessory kits offer an easy way to expand any CritterTrail habitat. Accessory kits offer a great way to expand your pets living space to create the ultimate habitat. The universally connectable kits are designed to provide a safe nesting area for curious critters and promote exploration, exercise, and healthy habits. Allows for expansion of CritterTrail habitats Includes fun nel Connector tubes rings and loop d loops Universally