CritterTrail Fun-nel Tubes attach directly to each other and to the inside and outside of your CritterTrail home. If you can imagine it, you can build it with CritterTrail Fun-nels! The tubes are available in four colors and in a variety of shapes and sizes so you can create a huge playground for your pet. Our 10" Tube is perfect when expanding from the roof top of your CritterTrail home. The 10" tube provides a safe climbing way into and out of CritterTrail homes. With CritterTrail Accessories, your imagination is your only limit.