This adapter is has a double ball joint secured by a ratcheted handle and two 5/8" (16mm) studs on either side. One stud is tapped with a 1/4"-20 female thread and the other has a 3/8"-16 female thread for a variety of mounting options. Each stud is milled with six flat surfaces to prevent your light fixture or any accessory with a baby receiver from rotating once the set-screw is secured.