The difference between C mount and CS mount is flange focal length that from lens mount to image plate.

C mount:
  Inside diameter: 25.4 mm
  Screw pitch: 0.794 mm
  Flange focal length: 17.526 mm
 
CS mount:
  Inside diameter: 25.4 mm
  Screw pitch: 0.794mm
  Flange focal length: 12.5mm
 
5 mm CS mount adapter ring is required when C mount lens attaching to CS mount lens camera.
CS mount lens cannot use for C mount lens due to the focal length difference and cannot get focus image.
 
Please check lens mount of camera when selecting lens.