Polyester material. Eco Friendly Tunnel Tube Rat Toy. superior quality. Designed for larger pets such as ferrets and rats. When hanging the diameter of the holes at either end is about 10cm (4?) . This clips to the cage via metal clips. This item is machine washable at low temperatures and these have been put through their paces by rats up and down the country who LOVE them! This is well suited as a toy for ferrets and rats.