I have 2 of the plug in heated pads that I have been using for the cats. Patches likes it when he's really cold, but usually moves off and snuggles with Shadow. Shadow does not like them at all. He has a special blanket that he only wants to sleep on. The plug in heated pads aren't supposed to be covered with a blanket. Also one of the heated pads is really hard. It's made of hard plastic and then has a fleece cover. The other one is soft but on the small side. So I found this heated disc. No electricity required. You just warm it up in the microwave and it stays warm for about 10 hours. I have used it the past 3 days and Shadow just loves it. I can place it under his favorite blanket and he can get right on top of it. My only complaint is that it is hard, but it does the trick. I heat it for 5 minutes and it has been staying warm for 10-12 hours. It was 22 degrees last night.