I have the gen 2 and for some weird reason only the right ear one hurts me after a while. I have small ears. I ordered the gen 3 and when I first opened the case and I saw them, I thought "oh geez, these things seem huge!' But if you look at one of the pics above, or if you have a pair of 2's and 3's and compare, you will see that the 2's are more round, while the 3's are more an oval but longer making them look bigger but are actually narrower.
A lot of people make the mistake that they have to *dig* these things into their ear canals to get good sound and that's why they end up hurting after a while. They are suppose to just *sit* in the ear canal, and push the sound to your ear drums. When I did this with the 3's it felt they were too loose but to my surprise after shaking my head vigorously, they did not fall out and the sound was very nice.
Everyone's ears are different of course, but if you are having pain make sure you don't dig them into your ears and just sit them, and turn them so that the stem is at an angle hooked into the small dip in at the bottom of your ear facing toward your nose. (Hard to explain). If you look in the tips app, it will show a diagram of how you are supposed to wear them.
GOOD LUCK!