I make a muslin bag to put the rice in and then make a bag from a fingertip towel to put over mine. I sew the end shut with long machine stitches, so when the outside gets dirty, I can take it off, wash it, and put it back on. That way the rice doesn't get wet. I keep the rice loose in the bag, so it conforms to my neck, shoulder, feet, etc. whichever needs the heat. I can't go to sleep with cold feet, so that's where I use mine the most.