From the website:
Dogs are curious, they want to know what’s happening out there!
Help satisfy their curiosity and make it possible for them to have a peek.
You can do just that with the PetPeek window:
The PetPeek™ window can easily make that possible.
The PetPeek™ window is a durable, clear, hard plastic dome 9.5 inches in diameter, with a black trim-ring and all necessary hardware for easy do-it-yourself installation into your wooden fence. It is an attractive addition to your fence.
Link - Thanks Blurb!