Did you know that many .flv files can have their video streams directly ported into a .mp4 container?
What do I mean? Take a box of paper clips for example, imagine first bending them strait, then bending them back into the shape of paper clips and then finally place them into a new box. That is kinda what other converters are doing: because some containers only accept paper clips of certain shape, or some container contains "irregular" paper clips that requires to be processed before placing into a new box.
But this converter simply takes the same paper clips in .flv and dumps them into .mp4, because those paper clips dont need to be reshaped in many cases.
You can do this with ffmpeg via Terminal fairly easily, but this App allows you to simply drag the .flv file onto the window, and it will create a .mp4 file of the same name inside the same folder directory. No need do complicated folder selection, or file renaming or video quality setting, etc. It even supports multiple files at once. Best of all, it is super fast!