This is the HS-645MG Metal-Geared, Coreless, Ball Bearing, Hi-Torque Servo from Hitec. This version of the servo has a universal connector which will fit Airtronics, JR, Hitec and Futaba receivers (be careful with the polarity of the connector for Futaba radios).

The specs on this servo are:

• Transit time: 0.24 sec/ 60 deg. @ 4.8V (0.20 sec/deg @ 6V)
• Torque: 107 oz/in @ 4.8V (133 oz/in @ 6V)
• Weight: 55.2g (1.94 oz)
• Length: 38mm (1.5″)
• Width: 20mm (0.8″)
• Height: 41mm (1.6″)