I ordered several bottles in different sizes for use in various locations at home and work. They are nice and lightweight and look very stylish. I will not be using them for hot drinks so this area remains untested by me. I'm sure there will be some small print somewhere as to what criteria the thermal claims are tested against but I do not think the bottles live up to their potential. During the recent spell of hot weather, I filled the 250ml bottle with chilled water from the fridge before going to bed so that I had access to a cold drink during the night. After about 6 hours I awoke and took a swig and found the water to be cold but certainly not chilled. This was indoors with an ambient temperature of about 20°C. I am yet to test outside during the heat of a summer sun but I am not expecting great things if I am to be honest. In sumary, they look good and talk the talk but not necessarily walk the walk.