4 Twist Lock: Our indoor outdoor cat door could be set to 4 modes by the twist lock with tabs: only exit, only entry, both entry and exit and fully locked, easy to control your pet when entering and exiting . Size: Outside size 27*23*5.5cm (L x W x H), Inside size: 19.5*18cm" (L x W), suitable for installation on doors and thin walls, suitable for cats more light than 11kg. Quiet: With the help of magnets and brushes, the panel does not come into direct contact with the plastic, which can reduce the noise caused by large cats going in and out. The transparent door panel for opening and closing ensures that pets can observe the indoor and outdoor environment at all times. Reduce your Heating Control Air Conditioning Costs:The doors do not can not be opened all the time, the cat can come and go freely in the wind, without the heat of the rooms in the house getting cold. Easy to Clean:The smooth plastic case allows to easily remove the stains brought by your cat from the outside. Note: best used indoors.