This is the Spektrum S651 7kg Steel Gear Standard Size Servo.

Spektrum RC S651 7Kg Metal Gear Servo. This waterproof servo is a replacement for a variety of Arrma models and is the updated version of the ADS-7M Servo. Package includes one servo, four grommets and hardware.

Specifications:

• Replaces: ADS-7M
  
• Torque:
• @6.0V: 88 oz-in (6.37kg-cm) 
• @7.4V: 103 oz-in (7.42kg-cm)
• Speed:
• @6.0V: 0.143 sec/60 deg 
• @7.4V: 0.122 sec/60 deg 
• Length: 1.58 in (40mm)
• Width: 0.79 in (20mm)
• Height: 1.55 in (39.4mm)
• Gear Type: Steel/Brass
• Waterproof: Yes
  
• Spline Count: 23T