This is the standard four hole nest which works great for hanging on a wall and providing a place for your birds to lay their eggs. Side Panels and perch brackets are galvanized; top, front and back partitions are plastic. Comes with removable plastic nest bottoms for easy cleaning. Perches flip up for to close off the nest boxes at night if necessary. Front opening is 7" x 11 1/2". This model uses nuts and bolts for construction. Experts recommend one nest box for each 4 laying hens.