The Brother MFC-7840W laser toner from Toner Refill Store is 100% guaranteed to meet or exceed your expections and surpass the print quality of the OEM (Original Equipment Manufacturer) Brother MFC-7840W laser toner. We also carry the compatible drum unit for the Brother MFC-7840W. The Brother toner cartridge can be replaced without replacing the Brother drum unit. The drum unit will need to be changed occassionaly, but will usually last between two to three cartridge replacements. Our Brother MFC-7840W high yield laser toner cartridge and drum units have a 'One Year 100% Satisfaction Guarantee'. The use of our compatible laser toner and drum units for the Brother MFC-7840W does not void your printer's warranty.