This is the KO Propo KR-411FH 2.4GHz FH-SS Receiver. The KR-411FH four channel micro receiver uses KO's Frequency Hopping Spread Spectrum system and is only compatible with the RF-903FH and RF-904FH modules.

Receiver Features:       

• Input voltage 4.8-7.4V
  
• Coaxial antenna wire for better range and noise filtering
  
• Small Footprint 28x18.3mm
  
• Quick binding
  
• Fail Safe Function
  
• 4 Channel System
  
• Operational lowest voltage 2.5V