Click to Activate, No Microwave or boiling water needed​Our gel packs are composed of water and sodium acetate (vinegar and baking soda). The durable outer casing is BPA-free and latex-free. When the internal disc is clicked, a reaction is set off, causing the liquid inside to immediately crystallize and heat up to approximately 130℉ (54℃) in seconds. ​Just click the coin disc for instant heat or refrigerate for a cold pack. No electricity or microwave required.Non-toxicLong-lasting heating padSafer than electric heating padsReusable over and over againInstant Activation Simply click the metal disc and you’ll have a soothing hot pack in seconds.To prolong the heating effectiveness, just wrap it up in a thin towel, cover under a blanket, or place under some clothes to reduce heat released away from the body. Safe & Non-toxic MaterialOur reusable hot cold pack contains sodium acetate & water and has a non-toxic and latex-free PVC casing. Safe for all ages. Easy to re-use​​Boil the packs for around 20 mins or until all crystals dissolved and the gel is clear again, let it cool to room temperature and it is ready to be activated again.If you don\'t see all the crystals completely boiled out, just add a minute or two as needed. Cold TreatmentPlace the gel pack in the refrigerator for 1-2 hours at its liquid state before applying cold therapy.The pack can remain in the refrigerator for an unlimited length of time without causing any damage.Note: DO NOT place packs in the freezer. Hands-free DesignPocket with Elastic strap allows the gel pack to be held in place during daily activities.