I used to use the sennheiser sports in ears, until I lost a part. They never fell out.
Then the adidas fins.. they always used to fall out. So in my last ditch attempt I thought I would try these..
After the first 30seconds of trying to use them I thought they would not fit and was thinking to return them. However after trying to the second time around, they fitted perfectly. You just have to get the twist correct, so it might take a little practice.
But after that.. fantastic.. did not fall out at all and I am talking with full pace sprints, as well as things like sqat jumps! Also the packaging comes with a guarentee, where you can contract the manufacturers via email to get custom fit buds if the ones supplied don't fit properly.
The mic/control part is a bit heavy, but it comes with a clip, so you just attach it to your T-shirt, which worked well for me and prevented it from swinging around.
I bought a pair in January and up until now they've been excellent. No matter how sweaty you get, the earphones stay put. You get 2 sets of red earphone covers in the box, so they should be a perfect fit for anyone. Very comfortable, but you can also hear ambient noise, which makes them safe for running outdoors. The mic button can be a bit fiddly but otherwise the mic is good. They lasted me four months, and then the right earphone stopped working, but the box says they come with a lifetime warranty. I'm hoping this was a one-off, as they would have got the full 5 stars otherwise, and my faulty ones get replaced.