Info Sure Thermal Soothing Heat Packs feature a natural palygorskite 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) and includes shaped back and shaped neck warmers for targeted comfort and relief. The thermal bead filling is palygorskite, a harmless and natural magnesium aluminium silicate mineral. In a powdered form, this abundant clay mineral is widely used in medicines that are formulated to remove acids and toxins from the digestive system. Microwave for soothing warmth or freeze for a relieving cold compress.