iCoolsoft M4R Converter for Mac is an audio edition and conversion tool. It was designed so that you can convert your video files to M4R files to use them as ringtones. M4R is the default format used in iOS devices for ringtone files. This app also supports other output formats like MP3, WAV, AC3, AAC, and a few others.
Graphically, you will notice that this app uses the same graphical user interface that you can find in other iCoolsoft video converters. Basically, this is a video converter with stripped down features. All the support for video files has been removed, but some of the features used for video conversion are still there. Some of them are the video editor and the subtitle selection menu. I tested iCoolsoft Ringtones Maker for Mac yesterday, and it is identical to this app. Both apps still are missing some features that are standard in ringtone makers, like automatic adding to iTunes, fade in and fade out effects and a waveform visualization mode.
The app does work well, though. I converted an MKV file to M4R and I trimmed it to a 30-second clip, which I later added to iTunes. Everything went as expected and the audio file played well on my iPhone.