The construction of this IEM is the best in its class. FiiO made the nozzle longer which results in better isolation. Comfort and ergonomics are quite admirable. This looks and feels like a 300$+ IEM. It comes with tons of tips and accessories like other high-end FH series IEMs from FiiO.
When I first listened to this I couldn't believe my ears! I saw positive reviews all around before purchasing this product. I didn't want to believe it, but the hype was real after all! The first thing I felt was "So this is what Hi-Res really sounds like?". The beryllium coated dynamic driver has an excellent bass response. A remarkable quantity of it too. Bass is tight, fast, and smooth. There is no bleed or bloat in the low end. Mids' quality is excellent too. Its very natural sounding and both male and female vocal sounds superb. I listen to a lot of technical metal,progressive rock and the fast double bass drums sound is breathtaking with these. This uses the Knowles 33518 BA for the high frequency. Which they also used in their FH1 series. I am personally a big fan of this BA and for me, this has the perfect balance. Great detail and resolution without sounding harsh. The sound stage and separation is way beyond its class.
I had the FH5 and while that has more sub-bass and "rumble" I like this pair more as this has a more "balanced sound' without sounding dull. An absolute no brainer for any price point. This is the true flagship killer.