For those who has a PRO CCS type camera. 25mm standard lens with Fix iris lens. This lens has 1/3" Format, C-Mount Type, 25mm, Focal Length. Viewable angle. If your camera can use both type of lens, then it doesnt matter which one to select. Check to see if your camera can use C or CS lens. Most cameras can use both C&CS lens and comes with C-Ring adapter. With the C-ring adapter twist onto your camera, then twist the lens onto the c-ring adapter.