I have been using this extension for about a week now with excellent results. It is fast, accurate and easy to use. The directions are somewhat vague and mention a "button" apparently on the YouTube video, tho I have never seen it on any video. I use this to convert the YT video to mp3 to listen to later on my mp3 player. Not sure if there is a limit on the length of a video to be converted. Bottom line: after some very disappointing experiences with other conversion extensions, this one is simply the best by far!