So, this is a "bi metal heat break" for 3D printers tailored for V6 model of Hot end and Heat sink, and similar.
Bi metal it means that the actual pipe/tube is a very low heat transfer metal (a hypodermal syringe needle a bit more hefty) that at both ends is welded into a piece of threaded copper that is a very good heat transfer metal, better than aluminium.
So that the lower threaded part of M6 thread transfers to the tube a lot of heat melting the filament before it goes in the printing nozzle, while the bare tube between copper ends is supposed to not transmit heat above (heat break) to the other copper piece of M7 thread that goes into the heat sink, with the clear purpose of keeping the filament in it from being melted, hence solid, reason for which the heat sink is cooled permanently (with air or liquid) and keeping that end of the heat break as cold as possible.
Theory is neat, practice is shit.
To start with the seller brags the cooper threaded ends are solid welded to the needle/pipe metal and will not separate.
Mine did, and this is crap, over 30USD paid for what?
Now I have to buy others, maybe from another seller, but I am afraid the producer is the same 'understandard' company.
Than I had my filament jam often in printing, and as I found out, is due to the needle/pipe, that is cut both ends but not funneled, causing the filament to cut itself in the sharp inner edges and get stuck.
I sorted it out by first drilling with a 4 mm drill for half a mm in the upper end of the heat break, than I used a small mill bit, conical, to polish that; 'mirror class', than another small router bit, spherical, to finish the polishing and shaping, creating thus a funneled entrance in the tube that starts at 4mm diameter and ends up whatever the tube it is, I guess 2 mm diameter. And the jamming stopped as by miracle.
In production with the propper maching settings (and they are acheap) this funneling that took me 10 minutes by hand with a 9Volt Makita drill, it would take them about one minute to do.
And the welding of the pipe/syringe needle to the copper part; done based on pressure shrinkage I assume, fitting hot copper parts expanded by heat over superfrozen pipe shrunk by cryogenisation, would hold far more if the pipe would not be polished on the outer side, on the contrary, should be not just rough, but also with striations (rifle style or similar).
Conclusion, if a Chinese company statest they did something like an European or Japanese company (or even an American one, thou they are more like the Chinese when it comes to quality) be sure they never understood the basics, the engineering sucks here and there, and the result is less than mediocre.