This is the quick-release clip for the OpenPilot CopterControl and CC3D cases. You also need the bottom part and the top part for the board of your choice. Note that you can order multiple clips to enable easy transfer of a board between different frames. More info here: http://wiki.openpilot.org/display/Doc/CopterControl+case and http://wiki.openpilot.org/display/Doc/CC3D+Case
CC3D complete set?