Original Equipment:Factory Original replacement ribbon cartridge is identical to the ribbon that is included with the purchase of new clocks, Models ES700 and ES900. It is also compatible with older clock models 175 and ATT310. Easy to Install:To replace an existing ribbon cartridge, just open the outer case of the clock and remove the existing ribbon, and snap the new ribbon in place.Longer Lasting:Designed by the manufacturer to last, with an auto-reverse feature that allows it to continue working for thousands of printings