Printer Essentials for HP 95 - HP Deskjet 5740 / 6540/ 6840 - Color High Yield - RM8766 Inkjet Cartridge
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HP 96 (C8767WN) (2 Pack) Inkjet Cartridge Replacement for HP Deskjet 5740, HP Deskjet 6540, HP Deskjet 6840 by Printel | Price: $11.62 | Cartridge Products | Partsmart
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HP Deskjet 6840 Ink Cartridge
HP Deskjet 6840 General Device Disassembly - iFixit Repair Guide