I've always been using the traditional rubber hot water bottles, but after reading about multiple incidents of them bursting and scalding people, I was looking for something safer and also less waste-producing (rubber ones are meant to be replaced every 2 to 5 years!). It takes a bit of getting used to yutanpos - they do get very heavy and of course are hard, so it's not possible to sleep cuddling them like I used to do with the rubber bottles. HOWEVER, they truly are a miracle invention if you live in a place with long winters and poorly isolated housing. They stay hot for HOURS after filling them - up to 12h when wrapped in some cover, up to 24h under a duvet. Pop one at the feet of your bed and you'll be toasty all night long. They're also amazing as a heated footstool, somehow the heat transfers through my feet to my entire body, so even when it gets really cold in the apartment, I can read / sit at my desk and not be freezing after 10 minutes. Super sustainable (if a little clunky), got 2 of them and love them!
