Wore them for a walk around the neighborhood on the coldest day this winter (right at -50 F), and my fingertips stayed plenty warm enough. Have done up to 12 miles of snowshoeing at 40 below, which is a much more realistic test, and didn't need handwarmers. I wear these snowmobiling as well, and don't need handwarmers unless it's colder than minus 15. My wife has a pair as well, and has done 8 to 10 hour days on a dogsled in the deep minus 20's, but does use handwarmers for the long days.