... solid will become cold. If you want reuse it, pls wrap it by towel, and put it into boiling water for around ... , then take it out from boiling water. 2).You can use it immediately or just put it there after taking ... inside again like the first time you use, it can heat again...so it is reuable on this way. ... ,Unpoisonous, Fit to all peple.It can be used for anywhere you want.Neck/waist/leg... Kinds of ...