I"ve tried rice, beans and flax… FLAX is by far superior in my opinion…it holds the heat longer… I like to put my heated flax warmer under a pillow at my side on a cold night.. it stays warm most of the night ! so soothing along my spine.. when I can't get my feet warmed up , I just push my warmer to my feet and ahhh..it warms them right up…… have fun making it… PS they make awesome Christmas gifts…even the little grandkids love them….