For those who has a PRO CCS type camera. This is our 4mm standard lens. Fix iris lens. If your camera can use both C & CS type lenses, then it doesnt matter which lens to use. This lens has 1/3" Format, C-Mount Type, 4mm, Focal Length, Up to 65% +/- Viewable angle. Choice of C or CS Lens. To use C-Lens, make sure your camera comes with a C-Ring adapter, you will need to twist that on to your camera before twisting on the C-Lens.