To choose the ideal length for your lamp shade, first measure the height of your lamp base, not including the lamp harp.  (If your lamp base does not take a harp, Alluminare lamp shades will not fit!)  In general, we have found that the best length for a lamp shade is about 2/3 the height of the lamp base.   Make sure, however, that you choose a shade length at least 2 inches longer than your lamp harp, so that the bulb, socket and other non-decorative base hardware is fully concealed from view.