Review (3/5): Not at all leak proof.
These were not at all leakproof. I had shampoo in one, and it leaked everyday on my trip. I'm not saying it leaked all over the place or anything, but the bag it travelled in was wet with shampoo, and after I took it out of the bag, I rinsed it off every day only to find it slippery with leaked shampoo the next day.
The suction cups almost worked for a day on shower tile, but then they failed, essentially making them of little worth to me.
On the other hand, the customer service is excellent: Even though the return window had (just) passed, Vumos was kind enough to refund my money for this product given my problems. So if you have an experience like mine, they won't just desert you!