Stainless steel inner lining + plastic outer shell [Automatic Magnetic Stirring Coffee Mug] No spoon needed! Simply pour your favorite powder (coffee, cocoa powder, hot chocolate, milk, protein shake, lemonade, broth, etc.) into the mug and press the button to mix evenly. Enjoy your drink anytime, anywhere - at home, in the office, at the gym, at school, or anywhere else. [USB Rechargeable] This rechargeable automatic stirring mug is equipped with a 400mAh battery. Thanks to its stirring technology, it can stir multiple times on a single charge. No need to change batteries; the battery compartment is waterproof for safer use. [Easy to Use] Press the automatic stirring button on the magnetic mug, and the stirring rod at the bottom will rotate and evenly mix dissolved substances and solvents. No splashing during stirring. Press again to stop stirring. The magnetic stirring rod is detachable, corrosion-resistant, easy to clean, tested, and securely attached to the bottom of the mug to prevent accidental swallowing. [Material and Cleaning] The inner layer of the automatic stirring mug is made of food-grade 304 stainless steel, and the outer layer is made of food-grade plastic. The double-layer design prevents burns to your hands when pouring boiling water. The cup is also easy to clean; simply rinse it with tap water. (Note: Hand wash only. Do not use in dishwashers or microwaves.)