An innovative alternative to traditional cat furniture, Catty Stacks are durable, and modular designer cat condos. Made in America from industrial-strength Corrugated Ultraboard™, Catty Stacks are recycled, recyclable, and long lasting. Create unique climbing structures to promote healthy exercise. Easily rearranged and relocated to maintain your cat’s interest. Great for one or many cats up to 20 pounds each. We all know cats LOVE boxes. Catty Stacks are better than boxes;