On the top of all of the ink cartridges, notice the letters "A" & B in between these letters is a carbon spot, not very noticable, but do assume it is there. Lexmark refurbished replacement cartridges recommends to use a sharp knife to scrape of this spot. I have no idea what this spot pertains to, but, I do believe that it only occurs with used refurbished ink cartridges. It is some sort of contact point that the printer uses to sent information to your computer for supply levels, and DATA to the cartridge. Once I scraped the spot off the cartridge, the supply level showed up as full on my computer, before it was reading only half full. The Cartidge now works like it should, where as before I was getting nothing.