(putting both to the test yet again on today's 95 degree
ride, and still finding the so-called "insulated" bottle
to be of little benefit).

http://www.polarbottle.com/features/chill-factor/

Nowhere near as good as a real thermos bottle, but a lot
better than a plain bottle.

=v= I've had much better luck with the Polar products in
frozen winters than in hot California weather. I can barely
abide the plasticky taste in winter, but certainly not after
it's been boiled all day. :^(
_Jym_