Please check the instructions before buying.Note: Vibration is invisible to the naked eye, only by putting it on your neck can you feel it at work. 1.Please settle 2 pcs AAA batteries( NOT Included );2. Switch on button .;3. Press ""on "" button . You will check the indicator display ""red', then change mode;4. Bring a neck massager around your neck;5. Press the button ""High"" until you feel an electric shock. This device uses electric current to stimulate muscles to achieve the purpose of massage. There are 6 modes in total. 15 strengths. The intensity is too low to feel noticeable. When the intensity reaches a certain level. You will feel an electric shock.Recently, many buyers say they don't work. After our verification, the situation is as follows. This massager has a total of 15 Level When the massager is turned on, the intensity may be too low to feel very small. At this time, you can press "high" to increase the intensity.