This DELL Latitude C840 Series AC Adapter is 100% compatable with the 85391 DELL Latitude C840 Series AC Adapter. Our batteries and accessories are made with high quality parts and are guaranteed to meet or exceed the original equipment manufacturers specifications at a reduced price. All batteries are tested for 100% quality control assurance. This DELL Latitude C840 Series AC Adapter includes a warranty to guarantee that it has no manufacturing defects.