Alright, so just that everybody know what to look out for if buying brake cables.
1: the bow of the the tube has to be as close to 90° as possible (right one)
2: the rubber coating of the steel cable and the inner sleeve should be thick, and operation (pushing cable in and out) should be as easy and smooth as possible
3: it should have a sturdy clamp and a ruber boot
4: the cut-off has to be perpendicular to the routing of the cable. In the picture the cables are oriented in the same way, the cut off has to be on the side (cable in front) and not on the top (cable in background)