Bark and commercial cork. Selection of bark (cork) from different tree species and examples of different uses of commercial cork. The bark examples are (clockwise from top left) beech bark (Fraxinus sp.), pine outer bark (Pinus sp.), elm outer bark (Ulmus sp., top right), elm inner bark (bottom right). Commercial cork is a material obtained from the cork oak (Quercus suber). It is predominately used to make various types of stoppers (centre and bottom) and is also used to make a type of floor covering (bottom left).