The addition of the new K&H Pet Products Straight Tunnel Toy provides cats with a simple place to play and hide when used alone. Made of polyester with sewn-in wire for stability and to hold its shape. Tunnel diameter is 9 inches. Collapses flat for storage. Not only is it great alone, but the versatility of these K&H Cat Tunnels also gives pet owners the ability to connect it to the lower holes of both the K&H Pet Products Kitty Towers (available in 2 or 3 level/sold separately) to create a larger playhouse. Connect more than one K&H Kitty Tower together for a more entertaining maze using the K&H Straight Cat Tunnel Toy. Designed by K&H with OVER 20 years of experience in creating safe, innovative, quality products for pets; one-year limited warranty.