This is the HPI SF-50WP Analog Waterproof Servo.

FEATURES
Metal gears for smooth operation without backlash
Heavy duty servo horn
Compatible with all Futaba radios and HPI RF receivers
Ideal for use as a steering servo

INCLUDES
HPI SF-50WP Analog Waterproof Servo with Universal Receiver Connector
Heavy duty servo horn, HPIC4098
Instruction Sheet

SPECIFICATIONS
Voltage: 4.8 - 6.0V
Torque: 166.6oz/in (12kg/cm) at 6.0V
Speed: 0.18 sec/60° at 6.0V
Dimensions: 1.2 x 0.83 x 1.1" (30.9 x 21 x 29mm)
Weight: 2.04oz (58g)