The Z-Finder Extender Frames allow you to further adjust the focal point of the Z-Finder by semi-permanently stacking the frames via a snap fit on to the skirt of the Z-Finder until the LCD screen is in focus for you. This is primarily for people who are farsighted or who wear reading glasses. This item includes 4 extender frames; all 4 extender frames will not be needed for everyone. It is best to test how many frames you need by stacking one at a time until the LCD is in focus for you. In order for the Extender Frames to lock properly, a new skirt is needed on the Z-Finder.