They work just fine. Most useful at temps well below freezing - anytime the freezing isotherm is in the bag instead of in the air (the place where the temperature gradient from the warm inside and the cold outside cross the freezing point). They can be used anytime, of course, to prevent or greatly reduce moisture migration from you into the bag. As they are an additional layer, they add some to the warmth of the bag, but the real reason for them is moisture control.<br><br>They are an "aquired taste".<br><br>Regards,<br><br>Scouter Tom