Patagonia Micro Puff Pants

Heaters. these are shell pants with synthetic insulation, Primaloft or some equivalent. they have a fairly loose fit. the waist adjusts via velcro tabs at each hip. they zip all the way up and down the side of each leg, so they are very easy to take off and put on.

for me, these pants are too warm for any extended/strenuous use unless it's truly arctic outside. they are fabulous for standing still or being around camp when it's cold, or putting on if you have an extended stop. they are lightweight (they weigh 17-20 oz, depending on what size you wear), they stuff well, and they are happily simple.

p.s - the outer shell fabric is very lightweight nylon, so if you anticipate any significant abrasion, you're better off with a more burly pair of shell pants worn as the outer layer. also, they aren't waterproof.  

Love these pants. They are warm enough to keep you toasty into the teen and have full side zips to aid in ventilation and temp control. The synthetic insulation does great in damp clammy conditions. Only downside is the lack of any pockets, but I still won't go climbing without them.