Thanks.
The purple tube has 4mm on the outside. I made a 6mm conical brass rod which I heated. Then I pulled the tube over it and dipped it in cold water. The larger diameter has stabilized. She mounted the cable without any problems. When heated, it behaved like a regular heat shrink band.
New patent.
A large one with a diameter of about 12 mm, after heating, shrunk to only 6-7 mm and that's it.