Gets cold instantly (3 seconds) for treatment of swelling, burns, nose bleeds, headaches, and other injuries requiring cold. No refrigeration needed. Remains cold (less that 40 degrees Fahrenheit) for a minimum of 15 minutes. Disposable. Durable, heavy plastic bags helps prevent accidental breaking and leakage. See-through bag makes accidental activation readily apparent. Instant action by impact, then shake gently.