Jonwrote a review of Black Diamond Mercury Mitten - Men's on January 3, 2018
Familiarity: I've used it several times
It's possible there are actual ovens sewn into these mittens. I'm out at 5 AM daily in the highlands of New Jersey during the Polar Vortex event of 2017/8 and my hands are almost sweating in these things.
Add a leash feature to these mittens and they get 6 stars.