The fit and finish were solid. The sound stage shallow, the highs (> 8kHz) seemed sharp, midrange was strong, and the bass was astonishingly anemic. As an electrical engineer and audiophile I do not believe that IEM 'burn-in' is a real phenomenon. I nonetheless followed the manufacturers instructions and detected zero change in output amplitude across the audio spectrum (~20 Hz - 18 kHz). In summary, great for phone calls, Zoom, or pod casts. Not so much for music if it has any bass content.
Toby53while I'll say in my experience generally burn in doesn't make a noticeable change there are times when it can change a lot
I burned in my Shuoer Tapes for a week which made them go from unusable for more than 5 mins (excessive treble painful to listen to) to usable for a reasonable listening session (1-2 hours)
and my Blon BL05s's 3 days of burn in made them go from muddy distorted bass that also distorted the mids to clean bass that no longer effected mids