The FS5115M is a standard-size analog servo from FEETECH that has an all-metal gear train and delivers extra-high torque normally associated with much more expensive or larger servos. Servo horns and associated hardware are included. This servo can work with both 5 V and 3.3 V servo signals.
Key specs at 6 V: 0.16 sec/60°, 215 oz-in (15.5 kg-cm), 58 g.
More technical information at Pololu.