I have one of those Polar brand insulated bottles they sell at all the bike shops ard here, and believe me, they don't work. at all. they just reduce the amt of fluid u can carry in the same bottle. Please don't waste yr money. It might be better to just fill the bottles 2/3 full and freeze them on their sides. bring one frozen bottle and one reg bottle so by the middle of the ride, the one remaining bottle is still cool and drinkable.