pipe union

It is a small connector that is shaped like a metal or plastic hexagon with a threaded hole.
Used to secure and tighten a bolt, or other threaded fastener in place.
In terms of mechanical and plumbing systems, a pipe nut is a type of connection that is used to connect two pipes to each other. It enables easy connection and disconnection of pipes without the need to cut them or permanently damage them. And they are usually used in situations that require regular maintenance.