Hey Guys Today days video calling is very little thing as compare to old times.Video calling is very helpful to people who are always want face to face conversation like interviews or business meeting etc etc. I am using this app from last 4 months and I don’t even any problem with duo.This app is purely free to install and anyone can install this app to smartphone or iOS.Basically duo has features better than other video calling app.Main quality of duo is that it don’t even lag while calling.It also works in slow connection.If you have slow internet connection don’t worry it will work absolutely fine but it will low down the quality of video.You can’t call any other person if you have slow internet connection in other video calling apps.It is the best app I had ever used.You must try it. Regards Friends