This is the HSR-1425CR Continuous Rotation Robotic Servo from Hitec.

FEATURES: 360° continuous rotation Dual ball bearing equipped motor

INCLUDES: HSR-1425CR Robotic Servo with Hitec/JR/Z connector 0.94" (24mm) diameter round horn four gromments, four eyelets and four 2x15mm mounting screws

REQUIRES: Installing in robot and connecting to receiver and linkage

SPECS: Operating Voltage: 4.8 - 6.0V Operating Speed: 43.4 RPM +10% Output Torque: 38.88 oz-in (2.8 kg-cm) Weight: 0.33oz (41.7g) Size: 1.59 x 0.77 x 1.44" (40.6 x 19.8 x 36.6mm)  

BOX DIMENSIONS: 2.00" W. X 1.88" H. X 2.50" L. BOX WEIGHT: .12 LBS.