I used google translate, lol. I've never seen round ones myself. I used to work electrical construction, and we used these rod couplings, and threaded rod to hang electrical conduit in the ceiling. That's how I first knew of these. If you can't find a threaded pipe and cap just get a straight piece of metal pipe about 16cm x 6.5cm then have a flat piece of steel welded on one end. It would serve the same purpose as a threaded cap and pipe if you boxed in one end like this.