As I told Annie, the on and off switch is unreliable. Sometimes it took several toggles back and forth to get it on. Sometimes while it was on then it suddenly went out! Apparently it is an electrical contact issue. Hopefully mine is just an isolated case. Also the on and off sign on the switch is very difficult to read. When the scope dangles on your neck, it turns in all directions. I have to pick up the bell to see whether it is on or off. I should be color coded. Hopefully this will help to improve this scope in the future. When it works, it works fine !