I have tried so many different types of nesting boxes. Almost addicted to the trial and error process. I believe I am finally content with these homemade metal boxes. Inside is 14 x 14. Inside height is almost 18". Sharply sloped roof with heavy overhang to keep them in the shadows. It was clearly a success. The next morning after installing, we received 10/12 production all in the boxes. Our girls look so happy.