Top principle, durability flop

This model I had ordered the first and was initially enthusiastic about the effect. My arm and joint pain subsided a few applications significantly. Unfortunately I had after 14 days notice that the term always non-circular and "rough" was. So I sent the product back and ordered from the same manufacturer, the higher grade model with tachometer, unfortunately, also showed after 3 weeks here rattle and vibrate at high speeds!