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ORFS fittings are becoming the most popular international fitting type used on global OEM machines due to their high level of sealing and their good vibration resistance. The fittings use the O-ring compression mechanism to seal. The female fittings have flat faces and straight threaded UNF swivel nuts. The male fittings have the O-ring in a groove in the flat face.
MALE: The measurements for the male are taken from the outside of the threads.
FEMALE: For the Female, the measurement is taken from the inside of the threads.
The below diagram shows both where to take measurements from and the size dimensions.