I just bought some this year. I got those that have rechargeable batteries. They were a cheap brand from Amazon Warehouse I bought on a whim in the middle of summer. I tried them for the first time deer hunting, and they worked great! Waited until I started to feel cold, then turned them on the lowest setting, and ran them til my toes warmed up. Used very little battery, and were quite comfy. Some have a remote or a phone app to turn on and off, which might be nice since I need to dig through layers to get to the socks and turn them on or off. I looked today and they have them for about $25 I paid less, but that kind of thin is cheapest in mid summer. They are not the greatest sock ever, but like I said, I bought them on a whim and I am glad I did.