A 6409-08 | #8 SAE/ORB hex socket plug is a type of hydraulic fitting designed to seal off an open port in a hydraulic system. The fitting consists of a hexagonal-shaped plug with an O-ring boss (ORB) thread and a socket for a hex wrench. The #8 SAE/ORB designation refers to the size of the fitting's threads, which are compatible with an O-ring boss port of a #8 SAE size.