I have a situation where my feet and hands get uncomfortably cold. I typically would use space-heaters (when I can) while I work but that's not always allowed, nor always practical. I decided to give these socks a try.
Before I start, I will say the instructions were for a totally different "model". Mine had three heat settings denoted by 1, 2, or 3 blue "dots". Also, the instructions don't stay how to turn them on or off.
Use the cord provided and plug the usb side into a usb wall plug (or something like that). Connect both micro-USB plugs to the batteries. Blinking means they're charging. Solid color means they're charged. When you're done, put the socks on first and then plug them on. Hold down the button for about 3 seconds to turn on. Mine turns on automatically to high (three dots) but within 10 minutes automatically goes down to 2. Odd. To turn them off, hold the button again. Tapping the button toggles the heat setting.
WARMTH: There are three options for heat which I mentioned above. I see NO reason to use anything besides high. High is not that hot FOR ME. I suppose it might get hot for people whose feet generate heat. Since mine do not, I always have mine on high. If you're wearing them around your house, you'll get a warmer experience if you put another pair of socks over them.
BATTERY LIFE: about 5 hour on the high setting.
COMFORT: Weird. They're like men's dress socks. That said, my female 7.5 foot fits in them well enough... and I pull them up over my full calf. The bottoms are stiff (where the heating pad is on the ball of the foot) and they're a little awkward. I tried to wear them in knee-high boots but they didn't fit with the battery. They feel a little awkward in shoes but I suppose it's better than your feet getting cold.
All in all I'm glad I got them but I do wish they were a bit more comfortable. I can see that there's no good location for a battery pack so the pouch exists in the least obtrusive area.
I am amazed that they can function after a whirl in the washing machine but so far I've washed them twice. I do not wash them after every use. First, my feet definitely aren't sweating if I need socks to keep them warm. Second, every time I wash them I'm terrified they'll break.
If they do I'll return and update my review.