This 6mm fixed focus lens fits C-mount
CS-Mount, C-Mount Cameras & Lenses
C- and CS-mount lenses are standard equipment on many
traditional CCTV cameras. The two type of lenses differ in how
they are mounted. The distance from the surface where the lens comes in contact with the camera to the focal point (the "flange back") of a CS-mount lens is 12.5mm (0.492"). This is 5mm shorter than a C-mount lens. Most professional cameras are CS-mount cameras and include a C-ring, so they can us a C-mount lens OR a CS-mount lens. You can't use a C-mount camera with a CS-mount lens
- the lens won't fit.