This is a replacement Spektrum SRX200 2-Channel 2.4GHz FHSS Receiver. This receiver comes included with the Spektrum STX2 Transmitter System (SPMSTX200).

The SRX200 Receiver has a special water-resistant coating on the electronics to ensure reliable performance in higher than average moisture conditions. This conformal coating can offer mild protection from light drops of water. 

Specifications: 
Type: FHSS 2.4GHz protocol 
Dimensions (LxWxH): 35.8 x 23.6 x 14.3 mm) 
Antenna Length: 8.27 in 
Channels: 
Weight: 8.8g 
Band: 2.4GHz 
Voltage Range: 3.5–9.6V

NOTE: The STX2 transmitter and SRX200 receiver utilize the FHSS 2.4GHz protocol and are NOT compatible with Spektrum DSM, DSM2 or DSMR transmitter or receivers.