Best iem, in ear monitor head set for around mid 300$. Compare with my old over ear monitor head set audio Technica M70x ($300) the ie 400 pro surprisly pick up more details. Bass is more impactful then M70x, but not over it. M70x feel flat in high to end and that it is why I bought it as a monitor headphone to use for editing sound. Ie 400 pro have warm and natura breathing sound. It surprise me a 7mm single dynamic can pickup more details then my over ear monitor headphone. And I don't feel it when I'm wearing it, it is so light, and ergonomic design.
Great sound, Nice fit.