MICR toner cartridge is designed for use with HP LaserJet 4250 & 4350 series Intelligent Printers: 4250, 4250n, 4250tn, 4250dtn, 4250dtnsl, 4350n, 4350tn, 4350dtn & 4350dtnsl. Cartridge contains magnetic image character-recognition ink for security purposes in printing checks. Smart print cartridge is estimated to yield 20,000 pages at 5 percent coverage.