This is the bottom part of the OpenPilot CopterControl CC3D case. You also need the top part (CC3DCase upper) and (optionally) the base clip (Case base 1 v1). Note that this case is for the CC3D only. The base clip is common to both CC and CC3D versions.
More info here: http://wiki.openpilot.org/display/Doc/CopterControl+case and http://wiki.openpilot.org/display/Doc/CC3D+Case
CC3D complete set?