The rechargeable battery is charged with a USB cable that arrives with your sleep mask. You charge it for only 2 hours and then you have 8 hours of usage. Bring it with you when you travel by train, bus, car, or aeroplane. Use it during your lunch break, at home, or whenever you need a power nap. The Bluetooth sleep mask will help you get the most out of your time. You will feel more rested after using it.