The Kimura Solo (Red IEMs) has a single dynamic driver. You’ll experience punchy bass and great spatial sound/soundstage for hearing where exactly the sound is.
The Kimura Duo (Blue IEMs) have both a dynamic driver and a balanced armature. You’ll get the great bass and soundstage of the Kimura Solo and then the Duo’s balanced armature adds detailed treble which can be great for audio cues such as footsteps in video games.
Both Solo and Duos come with two IEMs for both ears as well as the MMCX Kimura Microphone Cable and a variety of accessories!