Double glazing can be equipped with cat and dog flaps to let your pet come and leave at their own pace. They also help keep an eye on your pet while you are away. You can install a cat flap into an existing uPVC or double glazing sealed unit. But, https://cat-flap-installation-nea41997.kylieblog.com/31296524/installing-a-cat-flap-in-a-upvc-door-cost