Conbini Japan

Kairo Patch (カイロ) from Okamoto company (To put on white socks).
The Kairo is a patch that produces heat when it's opened for more than 5 hours.
Widely used in Japan in winter as well as in areas of the body with pain.
You can carry it in your hand or put it in your pocket.
Made in Japan.

Heat duration: Over 5 hours
Temperature: 41ºC Max, Average 38ºC
Size: 9cm x 7cm
Content: 1 patch
Composition: Iron powder, water, activated carbon, salt, superabsorbent polymer, vermiculite.