OVERVIEW
The 521SB allows you to plug in two 521 series remotes to rontrol the camera with both hands. For example, plug two 521PRO remotes into the 521SB and use the zoom wheel of one 521PRO to control zoom and the other to control focus. The 521SB is threaded with a 3/8'' and 1/4'' socket and supplied with a thumbscrew to mount directly to the Fig Rig crossbar.