Most of us have "sleep socks", a heavy pair only for use in our sleeping bags. Some of us use head coverings. I've found my best piece of sleep clothing is a light polyester fleece balaclava. It stays on and keeps my head and neck warm even in 10 F. temps. The head and neck do not have vasoconstriction in the blood vessels so act as a radiator in the cold. That is the part of your body that always gives off the most heat. (I can also use the balaclava it during the day if the weather gets extreme.) In the morning it's the last item of clothing I shed when getting dressed for the day. Often I keep it on during breakfast and until I'm ready to hunt. If it's cold, snowing hard or very cold and windy it stays on all day. It weighs very little and goes in a cargo or coat pocket, ready if needed in a snow storm. For an unexpected night away from camp it makes the night more bearable as i sit around my fire and wait for dawn. I also have a light fleece zip T-neck shirt for cold weather sleeping along with a pair of medium weight long john pants. And, believe it of not, wearing a pair of thin glove liners when sleeping also helps. Eric B.