There are two fairly popular types of hot water bottles that people use around the world: the floppy rubber version and the hard metal one. The Yutanpo Hot Water Bottle is made of an entirely different material and succeeds affording comfortable convenience where the others fall short.
Made by Masahiro Minami Design, this earthenware bed warmer is modeled in ceramic, forming a squashed disc shape with smooth bulging sides that are nice to the touch. A small inset hole is plugged with a metal cap, enabling access and helping to suggest the inner liquid's temperature.
It's simple to fill the Yutanpo Hot Water Bottle, and very easy to reheat the fluid within it, on certain types of stoves, in the oven or in the microwave. Especially when it's wrapped in its cover, it won't scorch you like some of its common counterparts, and it won't lose its warmth quickly either.