Dero Tech Rechargeable Digital Hearing Amplifiwr Open fit design, discreet invisible, super mini, lightweight Low power consumption long working hours, max Working Hours fully charged is 70 hours Super power BET, sounds volume switch,comfortable behind the ear and stays hidden Dramaticly enhance your ability to hear clearly and understand TVs, Phone calls, radios. Choose the correct volume which you feel comfortable and clearly, but pls note to adjust volume to the minimum before wearing and then increase volume gradually to avoid sudden increase in sound.