I use a combination of 1/2 rice and 1/2 buckwheat. You can mist it if you need moist heat. The buckwheat holds the heat a little better than just plain rice, and can also be used as a cold pack. I make neck warmers in a big C shape around 6 inches wide, and make a wiggly quilted line down the middle so the filling stays flatter, not as heavy, and stays evenly distributed. They work great, and no problem with bugs!