This is a poor quality product despite the marketing and the high price that lead the consumer think otherwise. After a few weeks of use I noticed 2 defects in the design and in the overall quality of the metal. Firstly, the clamp does not keep its grip on the arm because of the bad design; secondly, the bolt that is supposed to maintain the grip is of such bad quality that within a few weeks of normal use, the thread strips / breaks. The clamp can therefore nolonger be used. A real disappointment due to the manufactuer's minimal focus on quality and maximum focus on profit. I do not recommend PDP products and will never buy them again.