By testing on a 10 km run, the right earphone does not stay in my ear, not because of the size of the cap but due to the weight of the remote control that with every stride, gradually removed the right earphone . The earpiece left with no remote control remains in the ear.
The reproduced sound is decent, the functionality of the remote also (micro, buttons ...). The headphones are therefore of good quality for the price (bought 28) but not for a racing type of sport where the body is in constant motion.