Nevertheless I decided to buy the key. In addition, I put myself at the hardware store too a fitting nut for about 4. Then the cheerful tire changes could begin.
I have dismantled a total of 3 sets of tires and remounted. The key here is great in the hand. I have not measured it, but purely from feeling the torque specifications are correctly implemented (compared with other keys). I have always used only the extension but works fine and has kept. I did not feel that this would break / tear just off a little more pressure!
CONCLUSION: For the money, a strong buy recommendation!