If you're looking for a cat door tunnel, then you have a couple of different options to choose between. Interior cat door tunnels are really practical if you want to give your cat easy access to the litter box or in between rooms in your home. It's pretty easy to set up one of these cat pet door tunnels, and they are available in various sizes, so there shouldn't be a problem finding one that fits your particular needs just right.
Some of these cat tunnels allow you the flexibility to set the door at various settings such as: closed, open, exit but not enter as well as enter but not exit. This can really be a practical and useful feature if you want more control over the movement of your cat or small dog. So if you're in the market for a practical cat door tunnel or other pet door, then you have plenty of options to choose between.
PetSafe Deluxe Indoor Cat Door
"PetSafe's Deluxe Cat Door offers convenience for owners and privacy for cats. Allows you to leave the door to the litter box room closed while offering your cat anytime access. Features a transparent flap with four adjustable access settings: open all the time, closed and locked, exit but not enter, enter but not exit. Flap opens and closes silently and accommodates cats up to 12 lbs. Includes easy-to-follow installation instructions and a manufacturer's lifetime warranty. For use on interior doors only."
can be found at petsafe.com