Harp Saddle Adapters are made to fit directly over a plastic lamp sockets allowing a harp to attach to it. This adapter will allow you to attach a shade harp and use nearly any replacement shade on that lamp. This is meant to be an alternative to the lampshade which has fitter already attached to it. You can now easily attach a harp to a lamp without one. The opening on this adapter is 1 9/16″ and fits the Medium Base (E26) lampholders. A plastic (UNO) ring is needed to hold the adapter tightly in place.