What is the MS number designated for cross flareless tube fitting?

The designation MS 21906 is specifically assigned to cross flareless tube fittings, which are essential components used in various fluid systems. This unique number indicates compliance with military specifications, ensuring a standard of quality and interoperability among fittings used in critical applications. Cross flareless fittings are designed to maintain a secure connection without the need for flares, which can be advantageous in terms of both installation and reliability, particularly in environments where space is limited or where vibrations are a concern.

In contrast, the other designated numbers represent different types of fittings or specifications not related to cross flareless configurations. Thus, MS 21906 stands out as the correct designation for this particular category, emphasizing its accuracy in identifying the necessary fitting type for specific fluid handling requirements.