A fiber optic adapter, sometimes also called a coupler, is a small device designed to terminate or link the fiber optic cables or fiber optic connectors between two fiber optic lines.
SN/UPC 4-port adapter is designed to fit through the same panel cutout defined for duplex LC adapters, allowing an instant 4x of the current module/panel connector density by simply removing the LC duplex adapters and installing the SN adapters.