湯たんぽといえば、私の幼少期はブリキ製でした。その後、プラスチック製になり、色は長らく赤でした。

それが、無印の湯たんぽは透明に近い白色でした。たくさんあったので、電気代や灯油が高騰しているなか、とても売れているようですね。
Hot water bottles were made of tin in my childhood. Later, they were made of plastic and were red in colour for a long time.
That said, Muji hot-water bottles were white, almost transparent. There were so many of them, and they seem to be selling very well in spite of the rising cost of electricity and paraffin.