This is a Mole Richardson Adapter: 3/8"-16 Female Thread to Baby (5/8") Receptor.
Adapters with varying sizes of studs, receptors, threads enable the user to mount existing fixtures to all brands and models of stands, grids, holders and pipes.
All efforts have been made to post exact images of these adapters. Many images are not available from Mole Richardson. Please call us to get help with selecting the correct adapter for your needs.