Duha wrote a review of Platypus Insulator Hydration System on January 17, 2013
Well It is very nicely made and sturdy, and great insulator. But I have pushed it to its limit as far as cold, and it was around 10 degree's. Froze part of the line and the mouth peace. I heard that you can blow the water back in the bladder after use to keep this from happening. It worked down to around 18 degree's with minor freezing though so I am still happy.