Carbon rod is solid carbon fibre stock. In bending it is many times stiffer than wooden dowel of the same diameter and far lighter than metal, which is why it becomes struts, wing spars, control-horn pivots and the load-bearing members of flying models.
The surface is smooth and dark enough that a length left visible on a finished model looks finished as it is, with no paint needed. What it will not tolerate is being levered or twisted, because the fibres run one way only.
