Package of 4 vents. Easy to install in wood. Not made for metal, glass, or PVC pipe. Fits in a 3 inch round hole. For soffit ventilation, display cases, spice racks and reptile cages. These small round vents are easy to install. They fit into the hole made by a drill type hole saw and are held in place by knobs on the side. They are used for ventilating soffits, display cases, insect and lizard cages. Package of 4 vents.