on 9 December 2013
Got these as well as medium sized, because I wasn't sure which ones would fit best (I wanted a tighter fit, for biking and snowboarding)
Usually I wear the standard silicone ones that came with my earbuds, either M or S as they both fit fine (although the fell off quite easily)
The S size fits great on my ears, and they definitely stay better in my ears.
I honestly can tell if the sound is changed, it's still outstanding!