The MG90S is a micro servo motor with metal gears. It's an upgrade of the SG90 with more torque and speed. The MG90S is ideal for RC airplanes, quadcopters, and robotic arms. 
Here are some specifications for the MG90S: 
 
Weight: 9 grams
Dimensions: 22.2 x 11.8 x 31 mm
Stall torque: 1.8 kgf·cm
Operating speed: 0.1 s/60 degree
Operating voltage: 4.8 V (~5V)
Working Torque: 2kg/Cm
Reaction Speed: 0.11
Receives and processes PWM signals faster and better
Sophisticated internal circuitry
Good torque, holding power, and faster updates in response to external forces
 
The MG90S can rotate approximately 90 degrees. It has metal gears, which means the gears are less likely to strip when the motor is jammed