This handy heat pack provides instant heat wherever & whenever you need it. To use simply activate it by flexing the metal disc until crystals form, the innovative design stays warm for up to 30 minutes. When used simply re-activate by placing in boiling water for 5-10 minutes until the crystal is fully dissolved once more. You can use it time & time again, making it ideal for those who struggle with poor circulation or for days out shopping. Also ideal for camping, fishing, hiking & golf, the heat pack measures 11 x 7cm.