81665-2 is a neoprene flange seal designed for use with shell size 17 sealed CPC (Circular Plastic Connector) circular connectors. This sealing accessory is made of black neoprene material and features outer dimensions of 1.500 inches (38.1 mm) and inner dimensions of 1.125 inches (28.58 mm). The flange seal is used with square flange receptacles in Series 1, Series 5, and Series 6 sealed CPC connectors to provide environmental protection. It is commonly used in commercial signal and power applications where reliable sealing is required for panel-mounted circular connectors.