I am a Danner fan. I have the Pronghorn and a heavier insulated boot by Danner of which I forget the "model". I have hunted eastern Montana. Lots of walking. Not at high altitude, but lots of steep sided washes, because it was going to be near or bleow 0F, I took the heavier boot. These 9" boots did great in temps down to about -10F. Stayed warm and no problems with support.