The following products are guaranteed to work in your Brother MFC-7840W printer:
Active filters
Jet Tec B2120HC Remanufactured Brother TN2120 Black High Capacity toner cartridges
Jet Tec B2120 Remanufactured Brother TN2120 Black toner cartridges
Jet Tec BD2100 Remanufactured Brother DR2100 Black drum unit
Jet Tec B2110 Remanufactured Brother TN2110 Black toner cartridges
