This Kupo baby 5/8" (16mm) stud 66mm Long quickly attaches to any of the mounting locations on either the 3 Way Clamp (KG900412) or 4 Way Clamp (KG900712) 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. The KG005712 is 2.6" (66mm) long.