Specialty materials: thermoplastic materials. This thermoplastic material can retain heat for longer than a traditional thermos. Can be used as an ice pack or cold water bottle. Please note that this is not suitable for microwave heating. Safe and easy to use: The hot water bottle is explosion-proof and leak-proof, suitable for daily use. Fill it with only two-thirds of 80-degree water. Product Highlights: Hot water bottles can maintain heat for a super long time. The surface helps maintain liquid temperature. Best assistant: This hot water bottle can relieve common pains such as joint diseases, muscle aches, colds and coughs, and menstrual cramps. It can also be used as a cold compress for someone with a fever or to reduce swelling in minor injuries.