FEETECH FT90R Digital Micro Continuous Rotation Servo
The FT90R is a digital micro servo that has been built by FEETECH specifically for continuous rotation, offering an inexpensive and easy way to get your small turret spinning or miniature robot moving, especially when paired with our 60×8mm wheels designed specifically for this servo. This servo can work with both 5 V and 3.3 V servo signals.
Key specs at 6 V: 170 RPM (no-load), 21 oz-in (1.5 kg-cm), 9 g
more info at the Pololu website