A twine retaining device for a baler includes a retaining disk, which can rotate about a shaft, and a retaining plate, which jointly delimit a retaining gap. The pressure sensor is contained in a cavity in a module housing. The aft-body is composed of a crown portion, a sole portion and optionally a ribbon section. In two illustrated embodiments of the bladed carrying structure the created cooling air flow is generally parallel to the rotational axis of the compact disc, and in a third embodiment of the bladed carrying structure the created cooling air flow is generally transverse to the rotational axis. A secondary branch is then introduced to extend from the primary branch and produce the branched carbon nanotube. A lens holder is disposed on the holder, and a lens is configured on the lens holder, substantially aligning to the transparent material and the sensing area.