An Epson Mono Ecotank or Monotank is a black and white printer intended for the office. This printer can print more affordably than an inkjet or laser printer. That's because an Ecotank printer doesn't use cartridges, but bottles of ink instead. An Ecotank printer includes ink for 5000 prints in black and white. The higher the number after the 'ET-', the more extensive the printer is. For example, an 'ET-M1' printer is a single function printer and an 'ET-M3' is an all-in-one with an ADF.