I never write reviews right after receiving a product. Especially audio products. I have to give them some time. Not to burn in, but I have to listen to music at least several hours. I really expected those IEMs to be better. And I don't compare them to Focal Elex or even AKG Q701. I wanted them to have comparable audio quality to my Sony MDR-1000X and they don't even come close. Even when my Sony headphones are off and connected via cable they are much much much better sounding than Tanchjim Oxygen. Also I try not to remember how long I had to wait for them. What is definitely the biggest flaw of those IEMs is annoying bad sounding sibilants. They are well made, they look good, they sit in my ears fine, but I just don't like the sound, especially those sibilants. I even bought official Tanchjim upgrade cable before I got those IEMs from Massdrop, because I was so sure they really would sound OK. Not recommended.