This listing is for a vintage Art Deco porcelain Porcelier single socket ceiling light.  It measures 4 1/2" across the shade fitter end... 4" inside measurement for the shade fit.  It measures 5 3/4" across the ceiling fitter end.  It is 2 5/8" tall.  The light needs rewired. There is a hole for a pull chain socket if you want... can also wire to a wall switch. The socket was changed at some point in time. One set screw is missing that holds the shade. There are a couple of small chips by the ceiling fitter rim... not too noticeable. There is no mounting hardware with this light.  This is a nice piece from a nice estate.  Thanks for looking!