This is the Sanwa RX-371W Waterproof 3-Channel 2.4GHz FHSS-2 Receiver. The RX-371W is a small, lightweight receiver that is compatible with all Sanwa 2.4GHz FHSS-2 frequency modulation surface transmitters. This receiver is waterproof and works equally well in cars, trucks and boats, and is a great option if you don't need more than three channels.
3-Channel Full-Range 2.4GHz FHSS-2 Frequency Modulation
Works Equally Well in Cars, Trucks and Boats
Compatible with all Sanwa/Airtronics 2.4GHz FHSS-2 Capable Surface Transmitters