About the product MULTI FUNCTIONAL HOT WATER BAG: Thermoplastic material that is odorless and recyclable. Advanced thermoplastic holds heat longer than traditional rubber bottles also works as an ice pack or cold water bottle. But please CAUTION: The hot water bottle is not suitable for Microwave oven heating. EASY TO USE- Wide mouth is easy to fill and the anti spurt lip prevent water spitting back out like those old rubber ones. Fill only to two-thirds capacity maximum. It's transparent. No more guesswork about how much hot water is inside. BEST ASSISTANT- The classic design of this classic home remedy. Treating sore muscles stress or cramps arthritis aches and pains stiff necks lower back pain menstrual cramps and other common aches and and can also double up as a cold compress for kids with fever or to reduce swelling for minor injuries. CARE INSTRUCTION- Grid texture makes skin contact safer and more comfortable.