Do you have cat doors for windows? Yes, there are window inserts as well as doors mounted on the glass. To install through glass, you will need to have the pane replaced locally. We sell a window kit for cat size pet doors, and this kit works with the AB10 and AB21 pet doors. These kits are low-cost and a good option for those who live in an apartment. The flap on the door will need replacement every 2-5 years, depending on usage and climate. The AB10 can be mounted through a glass pane. To install this door you will need to have the glass replaced – window glass is tempered and cannot be cut. Your local glass experts can make a pane with the right hole size. We also make custom window inserts with dog doors, and these start at $570. Measure your window and call customer service at 800-749-9609 from 10 AM to 4 PM, Monday – Friday. These inserts are a higher quality window option for those who want a door that will last for years.