HP Auto Duplex Unit for LaserJet 4200 and 4300 Series, save time, money, and paper when you use HPÆs two-sided printing accessory. The accessory prints both sides of the page automatically, so you can concentrate on more important work. Youll see budget savings because paper consumption is cut in half. HP two-sided printing is done automatically so you can get down to business and not hover over a printer or copy machine. When both sides of the page are used, final documents are less cumbersome and take up less space in your office or briefcase. Two-sided printing saves you money by cutting paper consumption in half.