The new Sure Thermal fleece covered soothing aromatherapy heat pack feature a natural silica bead filling as an improved alternative to wheat based products. This natural and proven thermal alternative gives a more hygienic and longer lasting product that is more suited to regular microwave heating and cooling cycles. The range has been carefully made to comply with BS8433:2004 (Microwaveable Personal Warmers). The bead filling is silicon dioxide, an abundant, harmless natural element forming quartz and widely used in its powdered form as a food additive (anti-caking agent E551). Microwave for soothing warmth or freeze for a relieving cold compress.