This is the Tactic TSX45 High Torque Metal Gear Servo.
Specifications: Voltage: 4.8V 6.0V Torque: 143 oz-in (10.3 kg-cm) 151 oz-in (10.9 kg-cm) Speed: 0.21 sec/60¡Æ 0.17 sec/60¡Æ Dimensions: 1.6 x 0.8 x1.5" (40 x 20 x 38mm) Weight: 1.8 oz (51 g)