This is a 3-pack of compatible Black Laser Toner Cartridges for HP LaserJet 2400 Series printers. It is designed to replace HP Q6511X toner cartridges for crisp detail, sharp text and clear graphics. MTI © printing products give you consistent, professional results at 40-60% of OEM prices. MTI © toner cartridges are engineered to exceed industry standards of high yield and exceptional quality, and guaranteed to perform with HP Laser Printers. Every cartridge is factory tested and ISO approved. We offer an exclusive 30-day customer satisfaction guarantee and 1-year warranty. Our dedicated customer care staff is available 9 a.m. to 7 p.m, Monday through Saturday, to answer any questions and provide technical support.