Standard Size Ultra High Torque Servo - TowerPro MG959

via Adafruit
$101.41
SKU AF-5298
This ultra high-torque standard servo can rotate approximately 90 degrees and is the most powerful servo we stock. You can use any servo code, hardware, or library to control these servos. Good for beginners who want to make stuff move without building a motor controller with feedback & gearbox. Comes with 4 horns as shown. 
To control with an Arduino, we suggest connecting the orange control wire to pin 9 or 10 and using the Servo library included with the Arduino IDE (see here for an example sketch). Position "0" (1.5ms pulse) is middle, "90" (~2ms pulse) is all the way to the right, "-90" (~1ms pulse) is all the way to the left.
Note that the default servo pulse widths (usually 1ms to 2ms) will not give a full range of motion on this servo. We recommend using manual pulse lengths if possible: check if you can set your servo controller to custom pulse lengths and try 0.75ms to 2.25ms. You can try shorter/longer pulses but be aware that if you go too far you could break your servo, so slowly try a wider range to characterize the servo response!