This is a compatible HP Q5945A - Black MICR Toner Cartridge (18000 Yield). MICR is an acronym for Magnetic Ink Character Recognition. MICR Cartridges are used for printing checks. Banks read magnetic ink differently than standard ink, which allows them to reliably process checks. Magnetic Ink Recognition Toner; Regular toner mixed with IRON OXIDE particles, recognized by scanning devises. Mainly used for Check printing and bar coding. Built with NEW drums and NEW components that match all ABA standards (American Bankers Association). For use in HP LaserJet 4345, 4345x, 4345xm, 4345xs, M4345, M4345x, M4345xm, M4345xs printers. Compatible with MICR Cartridges: Q5945A, Q5945X, THN-45A.