This is a Doman Micro Servo.

Features:

• 5g micro servo RC servo with coreless motor
• High precision plastic gears
• Select torque motor
• Long life Potentiometer
• Blue color
• Futaba, JR, SANWA, Hitec compatible
• 8bit Digital IC

Specifications:

• Operating Voltage: 4.8V-6.0V
• Speed:
  • 4.8v: 0.10 sec/60deg
  • 6.0v:0.08sec/60deg 
• Torque:
  • 4.8v: 0.9kg.cm
  • 6.0v: 1.1kg.cm
• Dimensions: 21.4mmX11.6mmX18mm
• Weight: 5g
• Motor: Coreless Motor
• Gear Type: plastic (POM gear)
• Ball Bearing: No
• Dead Band Width: 4usc
• Connector Type: JR
• Wire Length: 20cm
• Servo Type: Digital
• Rotation Angle: 90 Degrees

Includes:

• DM-S0050 Servo (1)
• Double Sided Servo Horn (1)
• 4-Arm Servo Horn (1)
• Single Sided Servo Horn (1)
• Round Servo Disk (1)
• Mounting Screws (3)