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
One year limited warranty through Futaba beginning at date of
purchase

INCLUDES: Futaba R304SB 2.4GHz FHSS 4-ch Receiver

SPECS:    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: 1.38 x 0.91 x 0.33" (35.1 x 23.2 x 8.5mm)
Weight: 0.23oz (6.5g)
Antenna Length: 7-1/2"

COMMENTS: Caution, Do not cut, bend or bundle receiver antenna. Protect
receiver from vibration and moisture.
Manual can be accessed at
http://manuals.hobbico.com/fut/r304sb-manual.pdf