Combination of plastic and rubber washers with a flap designed to act as a valve for water exit out of your boat. Mount on the transom, slightly above the boat's water line. Diameter is 2-3/4".

 PROP 65 WARNING: This product may contain chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. Wash hands after handling. For more information, visit www.P65Warnings.ca.gov