Our birdhouses are hand-thrown from high-fired stoneware clay. The 7/8 in. opening is made with a round punch to make it uniform for birds the size of wrens, finches and chickadees, etc. A short clay perch is added to keep predator birds from bothering newborn babies. The house is bisque fired, glazed and high fired to 2,200 degrees making it suitable for year-around outdoor use. It hangs from a solid copper wire. The eggs approximate size is 6in. tall and 4in. wide. The birds will love building a nest and making this their new home.