This is the unidirectional version. However, one cannot speak of active noise cancelling in this context. The cardioid characteristic of the mic simply ensures that sound hitting the mic from the side and from behind is picked up much more quietly, which emphasises the speech (or the sound from the front). More detailed information on the manufacturer's website: http://www.modmic.com/pages/microphone-patterns
The microphone adheres magnetically to the small holder, which is fixed to the headphones. This means that the microphone should be easy to install and remove on a daily basis.