Our custom designed Wood Duck nesting houses are proven to improve population growth. The depth of the nesting houses provides predator protection to hens nesting their young. It is also suitable for Hooded Merganser, other cavity nesting ducks and some owls. Our family has been building these conservation boxes for over 40 years, with excellent results, year after year. Wooden post installation hardware included with each unit. (4) 2" screws (T20 torx), and (4) washers. Instruction guide provided for installation, maintenance, and species information. Approx. Dimensions: 19.5" x 11.5" x 11.5" Entrance hole dimensions: 3" x 4" Material: Cedar Each build is crafted individually by hand from raw Western Red Cedar which is naturally resistant to rot, decay, and insects. No chemicals or solvents used.