Furthermore, the knee pad is quite uncomfortable, it is obviously filled with air. When it is supported only with a knee, then pushes it through the pillow to the floor. (To have the hardware store for 2 euros) A knee cushion of foam is much more convenient.
And finally: The suction cups are of low quality. You have every single press firmly so that the mat does not slip in the bathtub. In addition, according to the suction force can after some time, so that now no longer adhere some of the suction cups.
Overall, I can not make a recommendation.