I’m a mail carrier and work outside for 6-9 hours 6 days a week in temperatures down to -33 windchill. Most winters are 25-40 degrees here. I bought these hoping to avoid buying 100 or more of the disposable hand warmers and saving money. These work IF they are kept warm, like in a very well insulated pocket and not exposed to the cold. On low I will get about 4 hours in 30-40 degree temps if it stays in a pocket or in a thick, fleece hat (I carry spares for this purpose) and I just grab it in between streets during delivery or to warm up in the icy trucks. I also keep one on low in an insulated lunch bag to keep spare gloves, my chargers, and cell phone from getting too cold. It works well there and lasts around 4- 6 hours. I tried keeping it on low, indoors and even at room temperature, fully charged, they do not last anywhere near 8 hours, much less 12.. DO NOT COUNT ON THESE if you’re camping or hunting. Batteries just drain fast in very cold temps and there’s no preventing it. The first day I used them I carried one in my hand on about half heat and it was dead within 90 minutes. They work very well the rest of the year as chargers. They do take a long time to charge up completely - I put them on the charger as soon as I come home and sometimes they’re not done by the time I go to bed. I do recommend them if you aren’t using them out in the open for more than an hour. The disposable hot hands work far better, and you can tuck them into gloves and they stay hot for at least 8 hours.

Perfect Christmas present for my hunter son in law to keep him warm while sitting in his stand.

1 out of 4 did not work.The other 3 worked great.

Excellent. Stay warm the whole round of golf.

They get really hot! I don't have any issue with power button, like other reviews mention. The flashlight works well too

Got for kids at college. Keep them in their jacket pockets when walking to class - work flawlessly.

I bought these for my son, who is in the Army. The push button for one of them got stuck the first time using it. He can't get it to come back out. Bad design.

I have purchased four, five....maybe more....I've lost count. Great gifts for others, and handy during the winter and while at the soccer fields with my kids.

Does not get warm. Waste of money

Work great and stay warm all day.