The Manfrotto 244N Variable Friction Magic Arm differs from the regular Magic Arm, in that the Variable Friction Arm allows partial locking in place of a light, grip, or a camera. This comes in handy when using a light or camera to track a subject. It is a pivot arm with a large locking knob. One end will support a light that has a baby (5/8") receptor. The other end is designed to fit into a Super Clamp socket, or other 5/8" receptor.
 
https://www.bhphotovideo.com/c/product/325444-REG/Manfrotto_244N_244N_Variable_Friction_Magic.html