Micro Receiver
 

I saw this on some robot website.
They use a lot of similar RC stuff like the Novak synth receiver and such.
Then I saw this one.
Just out of curiosity, would this work for 4 cell cars like a 1/12th?
I just though it was funny since it is slightly bigger than a penny!
Heres the info:

75Mhz Micro Receiver MBP-9G4

This is a small 6 gram, 4 channel, Universal FM/PPM micro receiver that uses standard 75MHz single conversion crystals. (Crystals not included). Perfect for US Ants (1lb.)

Key Features:
Universal transmitter compatibility. (Futaba, JR, Hi-Tec, Airtronics - Not compatible with some Pistol Style Radios)
Superior reception range. (over 1500 ft.)
Uses common 75MHz single conversion crystals.
Lightweight small construction and a flat design that saves space in your Ant-Weight.

Specifications:
Dimensions: 10 x 32 x 12 mm
Weight: 6 grams
Channels: 4
Range: 500 meters (over 1500 ft.)
Modulation: FM or PPM
Power: 3.5 - 7 volts
Connector: standard 3-pin (universal)
Signal shift: automatic, accepts (+) and (-) shift
Tuner Type: single conversion, narrow band
Plug Type: "S" connectors, universal for (Futaba, JR, Hitec, Airt-Z)
Compatibility: any FM or PPM transmitter

On their site it says:
Micro receivers are Not programed for use with 2 and 3 channel transmitters.
Use a 75MHz single conversion crystal set that matches your transmitter. (not included)