Warm and functional at 5.1 oz. I often hike in these thermal pants under my shorts. They dry out really fast and do a great job at keeping me warm.
On really cold nights, I'll wear them in my sleeping bag also.
Thermal pants available from Patagonia for $36.
I wear the mid-weights, at 5.1 oz, Theresa takes the expedition-weight womens small at 5.9 oz.