This is the Hitec HS-646WP High Voltage Analog Waterproof Ultra Torque Servo.
Waterproof-industry first IP67 rating, ranking these as among the most durable and reliable servos for wet conditions 3-pole motor. Dual ball bearings
INCLUDES: Hitec HS-646WP Servo with 1.02" (26mm) Single Arm, 2.3" (59mm) Double Arm, 1.6" (42mm) Four Point Horn, 0.98" (25mm) Single Arm and Mounting Hardware
SPECS: 6.0V Speed: 0.20 sec at 60°, Torque: 133oz/in (9.6kg/cm)7.4V Speed: 0.17 sec at 60°, Torque: 161 oz/in (11.6kg/cm)Size: 1.65 x 0.83 x 1.57" (41.8 x 21.0 x 40.0mm) Weight: 2.12oz (60g)