Curtain rod with quick fixing system

As I'm a fan of practical things that work well and without major complications, this is my "fast-on" solution to replace the original system that holds the rod of a curtain mounted on a shelf, which works very bad and is constantly falling .
This round rod is actually two, where one enters inside the other so that the system is extensible. In this case, the diameter of one is 8mm and the other is: 6.8mm.
The photos show the material needed and how the components are assembled.