Design
The phones are called 'in-ear' but are not canal phones. They have a small removable silicon tip or attachment that works as a grip. This arrangement is also good for exercising as the silicon tips prevent sweat from coming in contact with the expensive hardware. Three pairs of different sizes, namely small, medium and large are provided for varying fits. Though the protruding tips look to provide passive noise cancellation, such is not the case. Further, these headphones don't provide active noise cancellation. The headphones by default come with the medium sized tips. I tried all three and the medium sized worked well for me.
Medium sized tips that come on the headphones by default and large and small sized tips
Smaller sized headphones are generally referred to as earphones or earbuds. According to the size, Bose's in-ear headphones qualify as earphones but since they claim "Bose technologies offer a remarkable level of performance you'd expect from much larger headphones" they probably call them as headphones. But from now on I will refer to the 'Bose Headphones' as earphones. One of biggest problems one faces with earphones is that they keep falling off and the silicon tips are provided just for that. But with my experience of using it, the perfect fit doesn't last for long, most of the times. The earphones don't fall off completely but come to an undesirable loose position wherein you have to push them back in again.
The carry case has an internal design that prevents tangling of wires
Bundled along the earphones is a leather padded carry case to protect tips from catching dust. The silicon tips are particle magnets and catch dirt and dust quite easily. The internal design is such that it prevents tangling of earphone wires. The problem here is that it takes a fair deal of effort to wind the cable around the case and most of the times one ends up dumping the earphones with the mp3 player in the bag, especially while traveling.
I am delighted with these earphones; light, comfortable and very good bass. no problems with them staying put. I have noise cancelling headphones--that is not what I bought these- for. as usual a bit pricey, but that's Bose. 
