Pactrade Marine Boat Solar Powered Ventilator ODM, White Measuring 8 1/2" diameter and 2 3/4" h Ventilator cutout diameter 4 3/4" , screw hole to screw hole diameter 7.75" Installation on flat surface This water resistant 4" solar powered ventilation comes with intake & exhaust blades It moves up to 900 cu.ft./hr. of air when powered on solar and with a slight breeze provides passive ventilation at night