Cold Therapy: For cold therapy simply fill the ice bag two third full with ice and water to relieve discomfort from headaches bruises migraines muscle aches and swelling. Heat Therapy: For heat therapy add hot water (not boiling Notice: The temperature for hot water therapy is 50-60/122-140.) to help soothe an upset stomach migraine sinus and joint pain. Leak-proof Large Opening Lid: Superior Leak-resistant Cap with Large Cap Opening allows for easy filling of ice cubes or crushed ice.