Occasionally we will have customers call who say they can't fit their cartridge into their printer.  Many times it is because they are trying to put the incorrect cartridge into their printer.  However, sometimes it is due to the fact that there are small plastic guides on the inside of the printer that hold the cartridge in place, once inserted into the printer.  These guides are held in place by a screw.  If the screw gets loose, and the plastic guide shifts ever so slightly, it can make it difficult for the cartridge to slide into the printer.