The HP 739 DesignJet Printhead Replacement Kit (498N0A) is the genuine HP replacement printhead for the HP DesignJet T850 and T950 large-format printers, which print technical drawings, CAD plans, GIS maps and posters in architecture, engineering and construction offices. The printhead is the part that actually fires the ink onto the media; replacing it restores print quality when nozzles fail or image-quality diagnostics call for a new head. It uses HP thermal inkjet technology. The kit contains one printhead. The retail box measures 260.4 x 168.3 x 117.5 mm and the kit weighs 834 g. Follow the printer's on-screen replacement procedure, which guides you through removing the old head, fitting the new one and running alignment. Keep the printhead sealed in its packaging until installation, and store it within the conditions printed on the box.