This is the Savox SH-0255MG Digital Metal Gear Micro Servo.

Features:

• Over-spec refined design out performs ordinary micro size servo
• The Aluminum Case design looks good and allows for lower operating temperatures
• Precision metal gears forms a strong and solid framework
• Strict production and quality control of plastic components
• Totally Green – from materials to production, these servos are environmentally friendly
• Idea for CCPM and Rudder on 450 class heli's and Park Flier Airplane's

*NOTE: Certain combinations of receiver and ESC have been found to cause "Brown Out" issues when combined with Savox servos. An external BEC, or BEC stabilizing receiver capacitor may be needed for efficient, glitch free operation in low voltage electric applications. 

Specifications:  

• Speed @ 6.0V: 0.13 sec/60°
• Torque @ 6.0V: 54 oz-in / 3.9 kg-cm
• Weight: 15.8g
• Bearing: Single
• Type: Micro Plus    
• Gear: Metal
• Case: Aluminum
• Output Shaft: 21T Spline 
• Case Size (LxWxH): 22.8x12x29.4mm