Those Sahalie tights are the bomb, man. Mine weight 1.9 oz size M. They are footless hip-huggin' panty hose, is all, with a catch:
Normal panty hose, which we wore as youths in scouts for long underwear, and at soccer games in Seattle winters, tend to, well, you know, catch a thread and get some awful runs in them. It's terrible, coming across another fella on the trail and you're not looking your best.
So the Sahalie's are actually a pretty durable polypropylene. I go through about a pair every two years, and they are with me on every spring and fall trip, and many winter trips: I maybe get 50-60 nights out of them.
Can't beat the price, gotta love the weight, durability:weight ratio is good, but most important, the warmth:ratio is REALLY good.
Since I wear hiking pants most of the time, the normal mode in which I use the tights are over my hiking pants at night, in my bag. I prefer the feel of my hiking pants against my skin (Cloudveil Inertia fabric) than the polypropylene, which is clammy. Adding the tights OVER the pants keeps the sleeping bag cleaner (since my pants are usually muddy in the spring/fall) and drier (by preventing direct contact of my bag w/wet lower pant legs - so the polypro layer acts as a dispersion layer to help disperse and evap the moisture rather than wick it directly into my bag).
This item may graduate to my top five list pretty soon. I've used them for years and they always sneak their way into my gear lists.