https://www.roadfinetech.com/product/pneumatic-fittings/。

Pneumatic fittings provide the essential link between tubes, hoses and other components in a pneumatic system. Air fittings feature tighter seals and have lower pressure requirements than hydraulic fittings and are typically offered in various connector types.

Before making a connection, you will need to know the connection style, thread type, and the pipe size or thread size. The thread types must be compatible and the sizes must be the same in order for two components to mate properly.