does what it is supposed to! I bought this java sok to go on my glass camelbak water bottle. As expected, a glass bottle sweats, so I was hoping that this would help with that issue. The sok fits well enough – although not perfectly, but I am happy with it. I am not a take out cold drink drinker, but my daughters are, so I am going to be sure to have them try this sok out and perhaps it will make a great stocking stuffer for this Christmas!