I got my AirPods on Wednesday and absolutely love them buuuuuut........they kinda fit loose in my ears, which is what I was afraid of. I feel like I have weird ears/ear canals. The right fit better then the left but even just walking through the grocery store, I felt like i was adjusting them every couple minutes. I contemplated sending them back but I did some research. Long story short, I found a thread
on MacRumors from a couple years ago with a guy using a 3M Nexcare Waterproof Grip Tape.
I got mine in the mail today via Amazon and tried a couple different configurations for each ear and I'll be honest, they fit sooooo much better. They have no issue fitting in the case either.
I just wanted to throw this in here incase anyone has had a similar issue. I almost gave up on mine immediately but these will make them a daily fixture for me now.
Edit: This is the OPs picture from MacRumor. Mine look similar.