Strengths: The earpiece has many different sizes, and after trial and error you should find one that fits you. Two lengths of cable so good for armband and waist held players. Good build quality and the longest lasting I have ever had.
Weaknesses: Can be tricky to get the right combination of ear buds to get them to stay in. For the price it would have been good to have a connector to remove one ear piece, so you could have the choice to use single or both ear pieces connected. The sound controller is heavy, but I use an arm device so not an issue for me.
Overall: A good quality product, and the first ones I have felt comfortable with. I use them both in the gym, and out on cross-country solo runs. It would be good if one of the ear pieces detached so I could use the one with my running app when out on the roads, as if you just have one of the ear pieces in the other gets pulled out by the weight.