Features: Put it behind your right ear, Alerts when the for head lower in the degrees of 15 to 20. Especially suitable for long-distance driving or night driving. Driver safety alarm can help prevent accidents caused by driver's sleep when driving. Examine whether it is in the normal operation:it beeps when you are leaning your for head forward and makes no sound while sitting straight , it is at normal state. It is suitable for a wide range of people, such as night shifts, door guards, guards, television stations, radio stations, night broadcasts of check-in personnel, and security personnel. Specifications: Material:Plastic Size:Approx.7.5x5cm/2.95x1.97in Net Weight:23g Note: Please allow 1mm errors due to manual measurement. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1x Anti-Sleep Alarm