Kaytee Crinkly crackly fun for everyone. The 23 long silver Crinkle Tunnel encourages exploration and tunneling activity. Made of durable cotton and polyester material. Attach to other crinkle tunnels and Fuzz-E-Funnels for even more fun. Encourages healthy play and exercise. Additionally the Hide and Peek opening in the center of the tunnel is fun for both pets and pet parents.