The acronyms of the adapters:

F: Female

M: Male

SAE: Society of Automotive Engineers

SAE Society of Automotive Engineers

This term indicates the international organization which gave its name to the standard which it developed concerning the diameters of the quick couplings.

Translated literally, the Society of Automotive Engineers is an international organization that brings together engineers and business leaders from more than 97 countries to develop the automotive and vehicle sector at large.

The SAE standard was therefore implemented by this organization for the air conditioning sector. This standard is not based on a metric system since the diameters are measured in inches, this is how we can find values ​​such as:

  • 1/4 SAE is a quarter inch value
  • 3/8 SAE is worth three-eighths of an inch


This term designates a pitch system used for trapezoidal threading. This system is mainly used in Anglo-Saxon countries and is also expressed in inches. The peculiarity of ACME threads comes from its francs which form an angle of 29 °.

In automobile air conditioning we find most commonly:

1/2 ACME is a diameter of 12.7 millimeters