This solid steel adapter has a junior 1-1/8" (28mm) outer diameter and a baby 5/8" (16mm) interior receiver. This adapter has a set-screw with a knob to secure it to any baby pin or accessory. On the top of the adapter there is a bolt that secures it to the yoke of a lighting fixture for easy mounting into a junior receiver or onto a baby pin. This adapter is common for mounting PAR Can fixtures to light stands.