When I first got my MEST, I was really excited. Then I noticed the 2.5 mm plug didn't fit anything I had, including adapters. I ordered a 2.5 to 4.4 adapter as suggested but the 4.4 didn't fit anything, either. So I finally ordered a 2.5 to 3.5 and that worked. This is partially my error, of course, because I did not know there were so many size options for the plug. But this could have been made clear by the website and it wasn't.
The first time I tried the MEST, I was unimpressed. They were OK, but not great. But the longer I wore them, the more my hearing adapted and like a light going on, they became incredible. The sounds were rich and clear and I had little trouble understanding language (I wear hearing aids because of failing hearing). I became very impressed. So my advice is to give them a couple of days and you will notice how good the sound is!
The ear molds are large and totally fill the ear. I cannot hear anything outside of the MEST when they are inserted. This is good because no distracting ambient sounds can take away from the full experience. MUCH better than "over the ear" headphones!
Having worn hearing aids for more than 15 years, I was very disappointed to see that the MEST does not have cleaning options like my hearing aids. Wax build up in the ears can plug the holes and there is no easy way to clean them. I would suggest that this would be a major improvement for future development for two reasons: 1) wax build up can block and affect the sound received and 2) without cleaning, moisture build up can destroy inside components. Inside the ear moisture is salty and detrimental to electronics - I know from hearing aid experience.
One of the wires becomes detached from the ear mold frequently. It has a 2-prong plug and I can easily reconnect it, but this is not something that should happen. The prongs can go in either direction and it took a while to determine exactly how the mold should be oriented.
I do not like that these are made in China. I would much prefer to not buy anything from China but that is my personal preference.
It took 8 weeks from my order until the MEST arrived. That is a long time and part of that is because they were made in China and shipping was slow.
Overall, I can't rate these really high even though the sound is remarkable. Sound is a 5 star but all the other factors listed above is why I dropped it to a 3. There is much room for improvement in the design and buying experience.
Amazing customer service. Amazing sounding in ear monitor. Worth the wait.