During operation, the first side of the proof is printed from the roll and cut automatically by the printer. The SpinJet unit then reloads the printed cut sheet back into the Designjet, which prints the back side and delivers a complete 2-sided print in the printer's receiving tray. New SpinJet 2-sided Imposition Proofing Systems can come bundled with the HP Designjet 4000 Printer for a Turnkey Solution. However, existing HP Designjet devices that are in the field can be retrofitted to accommodate the SpinJet flipping accessory.