This is the Castle Link Quick Connect Duo from Castle Creations.
FEATURES: Installs between ESC and receiver and prevents loss of settings
when unplugging Castle controller from receiver
Detects the presence of Castle Link adapter on the free lead and
switches controller's signal line from receiver to Castle Link
Supports all Castle Link capable ESCs, but is designed specifically
for use with Castle ESCs featuring AUX wire technology
INCLUDES: Castle Link Quick Connect with Receiver Connector and Castle Link
Connector
