The Kupo 66mm long Stud (5/8,16mm) for 4/3 way clamp is designed to quickly attach to any of the mounting locations on either the 3 Way Clamp or 4 Way Clamp to accept any light fixture or accessory with a baby (5/8" - 16mm) receiver. All accessories for the 3 & 4 Way Clamp System have a proprietary notch that slides into one of the mounting locations and then is secured by turning the locking collar.