This is a compatible HP Q5942X - Black HY MICR Toner Cartridge (20000 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 4240, 4250, 4250dtn, 4250dtns, 4250n, 4250tn, 4350dtn, 4350dtnsl, 4350, 4350n, 4350tn, Troy 4250, 4350 MICR printers. Compatible with MICR Cartridges: Q5942A, Q5942X, THN-42A, THN-42X, 02-81136-001, 02-81135-001.