Child-sized rubber hot-water bottles contain less than 1 liter of water and are, as you may have guessed, designed explicitly for use by children. To prevent harm to children, these bottles also intentionally dissipate heat more quickly than other bottle sizes.
Mid-sized rubber hot-water bottles actually cover a large range of sizes: anything between 1 and 1.75 liters, to be exact.
For large heat-soothing needs, you’ll need a big rubber hot-water bottle. These standard (more like large) sized rubber hot-water bottles can hold up to 2 liters of water and are big enough to completely cover the abdomen or any similarly sized area of the body.
Rubber hot-water bottles are available in more than just flat surfaces, and each type of surface actually serves a specific purpose.