Slot entrance discourages sparrows. Entrance slot height is 1-1/4". Inside predator guard. Designed for excellent drainage and ventilation. Front wall tilts down for easy monitoring and clean out. Constructed of long-lasting western red cedar. Approved by the North American Bluebird Society. Dimensions: 5-1/2" W x 6-3/4" D x 10" H. From Songbird Essentials.