Pictured here you will see different types of Standard Factory Connections that are used on the end of tubing.
At the right you will see the standard 45 degree double flare with a male threaded SAE nut.
In the middle right you will see what we call Push Connect ends on the tubing.
In the middle left you will see what we call bump o'ring with a metric threaded nut.
At the left you will see metric buble flare without metric threaded nut.