I picked up this pair of headphones after getting frustrated with a Sony pair I had that just didn't fit on my head right. It turned out to be an excellent purchase.
These 'ear bud' headphones slip into your ear and stay there comfortably. They come with 3 different sizes of soft rubber domes which fit over the end of the ear bud and inside your ear. These domes help to block out sound that is not coming from inside the headphone, resulting in a clear, crisp audio experience. It is easy, when using these ear buds, to concentrate on what you are listening to since they block out distractions and outside noise.
This can be troublesome, however, if, for example, there are other people in the room that might talk to you, since you will not be able to hear them. In this situation I found myself having to pluck out one bud and ask the person to repeat what they had said. It is clear that these were designed for a solo, immersive audio experience, and they are fantastic for that.
If the buds are in your ears for too long they may become slightly uncomfortable, but this may be a good thing because it's good to take breaks from what you're doing anyway. Overall they are a solid product and I would recommend this style of headphone to everyone.