made 18 of these for xmas (along with 18 mug rugs and 18 headache masks). made muslin bags filled with flax seeds then pillowcases for each one (using the Missouri Quilt Co. you tube video). the warmer is heated separately, then dropped into its pillowcase. The cases get washed with the weekly laundry. everyone loved them. warmed their feet at bedtime. my sister borrowed her husband's and son's warmers to use for her aches and pains so I made her several more for her back, neck and knees.