Review (4/5): Do not put Paul Mitchell Super Skinny serum in this container!
I travel a lot an purchased these to replace some of my traditional travel bottles. So far, they've been good, with the exception of one that I used for Paul Mitchell Super Skinny Serum. There is some sort of chemical reaction that turned the serum into a hard gel, then the bladder separated from the cap and leaked all over. All of the other containers were fine (shampoo, conditioner, Ouidad serum, body lotion, etc.).