They work great and the warmth last about 10 hrs here in ...
928477
This is a phenomenal product!  I use it outside on my covered porch for my outdoor feral cat. H e sleeps on a chair so I placed it on that chair. It takes a few minutes to warm up, it's activated by their weight.  But it stays warm for as long as they're on it.  The pad cools down when not in use.  I have it plugged in 24/7 and it's not been a problem.  I just wish the cat would go in the house I purchased for him, then I could move his warm pad in there.  Oh well...  If you don't have access to an outlet I would suggest the Snugglesafe microwave disc.  They work great and the warmth last about 10 hrs here in NY.  Two great products I'm glad I found to keep my feral kitties warm this winter.
566176
Great product. They heat up a little slow but get pretty hot once it reaches it's peak temperature which took about 30 minutes. They lasted my whole session on the slopes. I used them while skiing and they were nice to have in my gloves and in my pockets!
2968441
I have bought off brand warmers before and wasn't pleased. I have bought Hot Hands before and never had a problem. The same holds true for these also. Although the "big" 5 x 7's are advertised as "body" warmers I found that these are perfect to stick in your coat pockets for the hands. They took about 15-20 minutes to warm up but lasted over 12 hours once they did.
2928851
Bought this a couple years ago so used them thru 2 new England winters. They seem to work well in water and snow. They're warm. Only issue I have with them is being too big and stiff so it's a bit hard to walk in them. I only use them when I'm shoveling snow....Works great for that.
4796
You'll love these warmers and you'll be amazed as to how hot they actually get when placed in your gloves or mittens.  If you leave your gloves rolled up with these inside, they will remain hot for 8 hours or more.  I don't go outside without these in the Winter and your hands will not sting from the below zero temps ever again.
2111493
They look cool and get the job done, but I would not wear them for an extended period of time in extreme weather. I live in Montreal, it's -30 today and they keep me warm for small trips outside.
3245744
These work well as commuter gloves on sub zero days - they will stay warm for two 40 minute commutes if you remember to disconnect the battery in the morning and reconnect when you're leaving in the evening - you will need to recharge before using again.  There are no heating elements in the fingers, so you may need to curl your fingers into your palms sometimes to keep your fingers warm.  My hands would get so cold on sub zero commutes that I would get nauseous - no more trouble with that with these gloves.  They're not attractive but when the temperature is 5 below no one will be worrying about how your gloves look.
1609034
These gloves are great! I've worn them everyday this winter when going outside pretty much. When I go to my car, work or grocery store, I have these on. They're very warm and very comfortable. I can wear them down to probably 10-20f by themselves, without needing another glove on top (unless I'm outside for very long periods of time without any activity). They're not great in high winds, but the wool in them makes them very warm otherwise. The touch screen pointer and thumb are very useful, and I've never had any issues using a small touch screen (like a phone) likewise works well with car head unit touchscreen, alarm panel touchscreen, tablets, etc. The size was a bit off I think: I usually wear a small and even with Outdoor Research Sensor gloves small fit me well - however with these I had to return the small for a medium. The fingers were too short for my fingers, but otherwise fit decently. I've had a few other glove liners and these are probably the warmest I have (although more thick), they fit well underneath Mechanix and Youngstown gloves, and give you the extra warmth you need to work down to 0. I definitely recommend these for anyone wanting a daily winter glove that's not bulky and works with touch devices.
3372116
I have always had a problem keeping my hands warm. I have tried more gloves than you can imagine, but these seem to do the trick. here in Vermont it gets really cold, I have a set of electric gloves when I have to be outside for the long term, but these work pretty good for the short term, an hour or so.
1255726
They work great for what i needed, however they don't last all night and they are not working by morning time, only about 6 hours of burn time.
1/3/2017 update: Had the worst ice storm and these lights are still working, see photo
561616
Keeps me warm working outside 10 hour days. For the price this thing will surprise you with it's warmth. Just make sure you layer up when the temperature reaches below zero.
948669
I purchased these for my daughter and she completely loves them! She said they are very warm and very light! She uses them on our farm to do chores in and right now it has been around 5-10deg Fahrenheit.

I would definitely refer these to someone.
4420204
Even though it takes a little time to install these it's worth it, they are so warm and toasty. I love'em.
1649791
work very well and are compact. Stay cold for hours
4870314
Purchased for my husband.  He likes to wear them at night after work.  They are very warm and perfect if he needs to go into the attached garage or to the end of the driveway to get the mail. His last pair were cheapies from Target which lasted less than 6 months before he wore through the inner lining.  Well worth the extra few bucks.
1971764
Very warm and very comfortable. To me, they are expensive but they are worth the investment.
2558991
Worked in 32F/0C weather on surveillance cameras. They do a petty good job keeping your hands warm, and giving you the necessary grip to grab things like small screws. Just know they're probably not ment to last long as the 2 days I worked with them, I noticed the finger tips began to wear pretty easily.