This principle refers to the basic design of the headphones i.e. the way the headsets couple to our ears and whether the back of the headphone part of the headset is open to the outside world or sealed against it. It can be in the ear (earbuds), on the ear (superaural) or over the ear (circumaural) and Open, Closed or Semi-open.

Characteristics of the device.

Where the product can be placed e.g. floor, wall.

The amount of devices that can be used with this product.

The material from which a thing is or can be made e.g. wood, plastic.

La couleur, p. ex. rouge, bleu, vert, noir, blanc.