C/CS mount lens is mostly for box camera. CS mount is 25mm diameter & 1mm screw thread. We have fixed focal and vari-focal CS lenses for selection. And we have a few C mount lenses for 1/2" box cameras.
Difference between CS and C mount lens:
Modern cameras and lenses are generally CS mount rather than C mount. With CS mount cameras both types of lenses can be used but the C mount lens requires a 5mm adapter ring to be fitted between the camera and lens to achieve a focused image. With C mount cameras it is not possible to use CS mount lenses as it is not physically possible to mount the lens close enough to the CCD to achieve a focused image.