This is the HSR-1425CR continuous rotation robotic servo from Hitec.
Includes: HSR-1425CR Robotic Servo with Hitec/JR/Z connector, 0.94 (24mm) diameter round horn, four grommets, four eyelets and four 2x15mm mounting screws
Requires: Installing in robot and connecting to receiver and linkage
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: 1.59x0.77x1.44" (40.6x19.8x36.6mm)