Soothes injuries by applying heat or cold to sore muscles.These hot/cold packs are microwave and freezer safe. Reusable and non-toxic. Instructions printed on reverse side. Please note: After freezing, stays cold for up to 3 hours. If dropped, the item will not shatter or break. After microwaving 30 seconds, the item will stay warm for 90 minutes. Condensation may potentially cause bubbling until cool. CAUTION: Product will be HOT after microwaving.