Why is the steam eye mask with thin heating core so flat and light?

This is a patented technology product of Shanghai Wenyou, a leading domestic self-heating enterprise, with patent number: ZL? 20 14 10 145975.3 。

As the name implies, it is a small square heating core, which is made of high-purity iron powder and other substances.

Its weight is only about 1.9g, which is very light and thin, and it will not press the eyeball when it is covered on the eyes.