TG4Z2813FCS-IR lens is a 2.8 to 12mm varifocal lens. Focal length adjustments can be made with a turn of the dial, virtually eliminating the cost and inventory problems associated with improper monofocal lens selection. This lens is a CS-Mount, comprised of all glass optics, come with locking setscrews and a durable metal barrel and mount, and are covered by a three year warranty. Aspherical optics provide excellent low light sensitivity. Infrared Lenses are designed for use with Day/Night cameras. They eliminate focus shift in night mode, especially in the presence of IR lighting.