When Lexmark sell you a new printer they only give you starter cartridges with it which hold a very small amount of ink in them Lexmark No.42 black and the Lexmark No.41 colour cartridges. I was using about 3 black and 2 colours cartridge per month and it was costing me a small fortune. I later found out that Lexmark do a higher yield versions of the No.42 and No.41 cartridges which cost only a few pounds more but hold far more ink in them than the starter cartridges which I was using before. What you need is a Lexmark No.44XL on the black which hold 22mls of ink rather than the 11mls of ink that is in the No.42 starter cartridge and on the colour what you should be using is a Lexmark No.43XL which holds 18mls rather than the 9mls which is in the No.41 colour starter cartridge. I can even go one better, I now use a company called advantage online who stock the Lexmark originals plus do a British premium compatible No.44XL and No.43XL cartridges which hold 27mls black and 27mls colour. I have used them a couple of times so far and have been quite impressed. I hope you don't fall into the Lexmark trap of selling a very good printer (X4850) at a very cheap price and then trying to charge you load of money for starter cartridges which are nearly empty.