These tube options allow DIN standard objectives to be used directly with either a DIN eyepiece or a C-mount camera. Tubes are the appropriate length for DIN standard. Any DIN objective can be mounted to either tube. Model #54-869 allows a DIN standard eyepiece to be used with an objective to make an ocular microscope. Model #54-868 allows the DIN objective to be mounted to a C-mount camera and achieve a primary magnification equal to the magnification of the objective. The field of view of the video system is equal to the sensor size divided by the magnification of the objective. For example, a 4X objective will yield a horizontal field of view of 1.6mm on a ½" sensor. Objectives and eyepieces are not included with tube assemblies.