Size M: Dia 12 inch,Length 51 inch | Two vents on the top so that cats can freely get in and out of the tunnel | Fun toy for cats to play:pet tunnel built-in crinkle paper, gives your kitty more ways to have fun,provides hours of exercise ,self-amusement and hiding away | Collapsible tunnel for compact storage and travel:this tunnel can be easily folded down and storage when not in use. Convenient and easy to take anywhere, so your pet is never bored | Removable ball that dangles for cats' enjoyment