Foundation vents allow air to enter and exit the crawlspace. This airflow helps to remove heat and moisture. The cross flow of air helps protect against foundation problems. Manual vent, Damper style, Plastic construction, 64 Square inches of Net Free Area airflow each. Standard 16-in x 8-in, Non-powered, Fights damp rot, Fights mold and mildew, Fights insect and pest infiltration