This is a handmade rice/flax seed bag that can be warmed up in the microwave for moist heat or put in the freezer. This foot bag will keep your feet nice and warm on those cold nights. Been working or on your feel all day, then let these relieve those aching soles. The bottom is a super soft flannel. You can also use this as a hand warmer. Just slide your hands right in.. The average heating time is 2-4min but can vary depending on the microwave. You can also warm up your bag in the oven at 325 for about 20min. Check it often during the warming process and shift it around so the rice can be evenly heated. Overheating can result in a burn so please be careful. When placing your bag in the freezer I recommend that they are put in a plastic bag to prevent the freezer smell from attaching to the fabric. Rice bags release moist heat that helps to aide with circulation and pain relief to sore muscles and joints. As your bag cools down, the heat becomes even more penetrating. The heat helps dilate blood vessels and increases the flow of oxygen and nutrients to help heal damaged tissue. It also decrease the transmission of pain signals to the brain and helps relieve discomfort. When used as a cold pack it works by reducing blood flow to a particular area which can significantly reduce inflammation and swelling that cause pain.