Cat Lovebox Indoor Cat Tree House 14.5W x 14.5L x 15H Cat Condos Box, 4 Pack Durable & Recyclable: The boxes are built with strong corrugated cardboard that can handle up to 20 LB cats, and built to withstand multiple cats jumping, playing and sleeping in or on top of the boxes. The boxes and the plastic components are manufactured to be fully recycled. Stackable and Modular: The boxes are made to be stacked and they can be stacked as high as you like. 8 Strong Rivet attachments are provided with each 4 pack order, 2 rivets on each panel is more than enough to hold boxes together. On each panel there is a perforated opening that can be opened to create interesting tunnels for cats to move around and play. Design & Style: Our boxes are designed specially and specifically to work with your home designs, Our boxes come in a range of prints to make sure you find a suitable design. Easy Assembly: The boxes are shipped flat but are very easy to assemble, a set of step by step instructions and a video is provided on how to assemble. Safety & Health: The opening of faces of the boxes are 8 in diameter, we have tested and made sure that cats are safe walking in and our of the boxes. The boxes act as a safe relaxing place to reduce anxiety.