To activate, simply bend stainless steel coin until it clicks. An exothermic reaction occurs creating hot ice crystals and warming up the pack to a comfortable 130 degrees for up to 1 hour (depending on size)
To reset for reuse, simply place heat pack in boiling water for 5-15 minutes (depending on size) until all ice crystals disappear. Remove from the pot and allow to cool!
Also great as a cold pack to reduce swelling after a workout. Place in refrigerator or ice chest (not freezer) for 15-20 minutes.