SAE O Ring Boss or UNF
Also known as SAE J514 Straight thread O-Ring Boss or SORB or UNF (=Unified National Fine)
This port connection is recommended by the NFPA for optimum leakage control in medium and high pressure hydraulic systems. The male connector has a straight thread and an O-Ring. The female port has a straight thread, a machined surface (minimum spot-face) and a chamfer to accept the O-Ring. The seal takes place by compressing the O-Ring into the chamfer. The threads hold the connection mechanically.