Inexpensive, quality good

This is neither cheap nor tool professional tool.
The quality is the key for the price more than reasonable.
The keys are heavy, well made and sit relatively fit with little play on the screws.
Break even at high torques or they do not bend.

The keys have a profile already, the power is transmitted in this case not directly on the corners of the screws, but something on the surface / edge, so that the screws can not be turned around more inside.
I think that makes sense to conserve the screws, especially as these keys are not quite as fit as professional tool.
I have a double ring spanner of Hazet for comparison, has absolutely on the screw no play, compared to the Heytec -key have a slightly greater tolerance, however, costs a Hazel-key even more than here all set.
For occasional use, it's not worth it to spend more money. In direct comparison to a Proxxon key the quality seems to be exactly the same.

After several tightened screws I can recommend the key, no damaged key / screws have occurred.
This kit is delivered in a simple cardboard box that does not last long, so you just have to organize themselves in a toolbox.