This is a pneumatic fitting.

It is a One-Touch (Push-to-Connect) type.

It is commonly made by SMC Corporation.

The fitting is a Straight Union connector.

It joins two tubes of different sizes.

Specifically, it connects a 4 mm tube to a 6 mm tube.

It is used to carry compressed air or water.

The connection is fast and requires no tools.

It belongs to the KQ2 series.

Dimension  : Approximate Value 

Weight2 g to 4 g (0.004 kg)

Length/Height~26 mm to 27.6 mm