This is a Spektrum RC SLR300 3-Channel SLT Receiver Single Protocol.

Specifications:

• Type: SLT Single Protocol Surface Receiver
• # of Channels: 3
• Modulation: FHSS
• Band: 2.4 GHz
• Length: 33.4mm
• Width: 21mm
• Height: 12.6mm
• Weight: 6g
• Voltage Range: 3.5–9.6V
• Antenna Length: 140mm