That's one of Echo's fan brackets. Plastic and foam with fans and batteries installed. The wires for the fans are on the back of the bracket, which itself can hide other wires (audio, mic, etc.) behind it in the neck tube. Contact "Echo" here with a PM or ask on his Ongoing FS thread. If you have a TK designation, he'll personalize yours. EvilBoy also has a popular fan option without the bracket.