Selecting the correct tube size ensures a secure, leak-free connection and reliable performance with DOT air brake fittings. Choose the tube diameter that best fits your application. If you don’t see the size you need, contact us and we’ll work with you to provide exactly what you’re looking for.

Alkon Metric Brass Push-to-Connect fittings follow a clear and consistent nomenclature for tube sizes, with the O.D. expressed in millimeters. For example, a 6mm tube corresponds to a “6” in the part number. Part number MAQ68-DOT-6X4 illustrates this sizing.


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5/32″ Tube Size

1/4″ Tube Size

3/8″ Tube Size

1/2″ Tube Size

5/8″ Tube Size

3/4″ Tube Size