Works great.
I've been using both bottles/bags(?) every night since they were delivered, and I simply love them. Haven't woken up at night due to cold bed issues. I normally fill the bag fresh about an hour before bed time and leave it under my comforter. Super warm and comfortable throughout the night. They stays in bed all day the next day, and they're still warm to touch when I get home after work. No leaks, very easy to handle, perfect size, no difficulty opening or closing.
Rating: 5 stars