The HP Laserjet 4SI laser toner from Toner Refill Store is 100% guaranteed to meet or exceed your expections and surpass the print quality of the OEM (Original Equipment Manufacturer) HP Laserjet 4SI. We also carry numerous compatible and remanufactured HP inkjet cartridges. Many HP Printers carry a High Yield cartridge and a Standard Yield cartridge. The High Yield cartridge will have an 'X' and the standard yield an 'A' at the end of the cartridge number. Toner Refill Store carries both the High Yield HP Toner Cartridges and the Standard Yield Toner Cartridges. Our HP Laserjet 4SI high yield laser toner cartridge have a 'One Year 100% Satisfaction Guarantee'. The use of our premium compatible laser toner cartridges for the HP Laserjet 4SI does not void your printer's warranty.