The Suppo SP-MG90 is a great little micro metal-gear servo, very similar to the TowerPro MG90, Hitec HS-65MG, or Corona 929MG. The SP-MG90 is a very smooth, precise, and reliable servo.
Note on servo model differences: the MG90S features more torque with slightly lower speed. The MG90 features faster speed but less torque. Use these specs when deciding which servo is best for your application.