This is the Futaba R304SB 2.4GHz FHSS 4-channel telemetry receiver.
Features: Used with the Futaba 4PLS, 4PX, and 4GRS 2.4GHz T-FHSS radios
Includes: Futaba R304SB 2.4GHz FHSS 4-ch Receiver
Power Requirement: 4.8-7.4V battery (dry cells cannot be used)
Receiving Frequency: 2.4GHz
System: T-FHSS (auto detection) with SBUS2 port
Dimensions: 1.38x0.91x0.33 (35.1x23.2x8.5mm)
Weight: 0.23oz (6.5g)
Antenna Length: 7-1/2
Note: Caution; do not cut, bend or bundle receiver antenna. Protect receiver from vibration and moisture.