Just buy it. So worth it.

This dog door definitely keeps the cold out. No drafts, gaps, or blowing open in heavy winds. It is a solid (opaque, not clear) canvas (?) flap, so if your dog has not used a dog door previously it could take some training. My two dogs had no issues using this door when we put it in my new house after years of the translucent flap petsafe door. It does make a loud clicking noise when they go in or out that some pets may not like.

Despite the strong seal on this door, it seems to be easy enough for a smaller pet to use. My little dog is about 12 lbs, Jack Russell/chihuahua, and she flies in and out all day long.
If you’re not very handy have this installed. Not an easy project. But even with paying for install this dog door is totally worth it.