The HobbyKing 6-Channel 2.4GHz Receiver provides a reliable link to your robot.
This is the V2, compatible with V2 transmitters (any sold after Oct 2010)

Receiver Size: 4.5x2.3x1.4cm (1.75x0.875x0.53")
Satellite Size: 2.7x1.7x0.7cm (1.03x0.66x0.25")
Weight with satellite receiver: 13grams (0.46oz)
Weight without satellite receiver: 8grams (0.28oz)
Operating Voltage: 5V - 7.4V
Bind multiple receivers to one transmitter.

Binding Instructions:
1. With power off, insert Bind Plug to Batt port of receiver.
2. Power on receiver. A red LED will begin to flash (it can be hard to see in bright lights)
3. Holding the transmitter's "Bind/Range Test" button turn it on.
4. When the receiver's red LED stops flashing, you can release the Bind button and unplug the Bind Plug from the receiver.