No matter what I tried, this product will not suction into our shower floor. Our floor is slightly sloped down towards the middle, and for this reason (or potentially because the floor is made of many small tiles?), the suction cups do not stick. Our drain became badly plugged with hair while using it, and we had to call a plumber.
This is not to say that the product wouldn't work for others--just beware if you have a sloped floor or a floor made of tiny tiles, it may not be the right product for you.