The product can correct the wrong posture of young people when reading, writing, standing or walking, especially useful for the students.User just needs to hang it on the ear and turn on the switch.It will alarm and warn user to pay attention to his posture when the distance between the eye and book is too shot.So it can help people to keep eyesight, guarding against short sight.It is not exaggerative to say that it is the most effective product which can guard against short sight up to now.This product also can prevent driver, guard and person on duty from dozing, reminding people to concentrate their mind and pay attention to safety etc.