An Ultimail requires two cartridges simultaneously in order to operate. This includes both cartridges. *Ask before you buy! We sell only genuine ink that is guaranteed to work on the listed postage meter. Not all inks are created equal. After much testing we sell only genuine factory inks, because refilled/refurbished cartridges have a horrible failure rate and short shelf life. For more information on how to know if your ink is genuine, contact a Whitaker specialist!