This is the S9551 High Torque Low Profile Digital Servo w/Coreless Motor for Aircraft and Car Use.

FEATURES: Digitally enhanced microprocessor cuts about half of the response time from transmitter input to servo reaction
Low profile allows for the servo to fit into wings and lie down in car chassis for less obstruction
Coreless motor
Metal gears
Dual ball-bearings
Black plastic case
Dust and water resistant (not waterproof)
One year limited warranty
Ideal for F3A aileron application and 1/10 scale electric touring car

INCLUDES: One S9551 Digital Low Profile Servo with 0.83" (21mm) diameter round horn, 1.7" (44mm) long T-shaped horn, four eylets, two rubber gromments (order FUTM2250 if mounting screws are needed)

SPECS: Speed: 0.14 sec/60° @ 4.8V 0.11 sec/60° @ 6.0V
Torque: 98 oz-in (7.0kg/cm) @ 4.8V 122 oz-in (8.8 kg-cm) @ 6.0V
Weight: 1.6oz (45g)
Dimensions: 1.6 x 0.8 x 1.0" (41 x 20 x 25mm)
Distance Between Mounting Hole Centers: 0.39" (10mm)
Horn Screw Size: 3x8mm

COMMENTS: S9551 Digital Servo Precautions, It is best to avoid long leads and Y-harnesses especially with standard grade wires. If problems are encountered, consider using heavy duty wire such as Futaba's Heavy Duty Series or Hobbico's Pro Series, minimizing lead lengths, and/or removing Y-harnesses. Current Drain: Futaba S9551 Servo is Specially Designed for High- Torque and High-Speed, Therefore Very High Current Drain Is Normal At Startup. For Ultimate Performance When Using This Servo, Please Review The Following Points.
(1) When Using Systems With the Battery Fail Safe Function it Has a Higher Cut-Off Voltage Setting Which Will Cause Shorter Operation Time.
(2) When Installing the Servo Please Check Pushrod Linkage To Make Sure There Is No Binding in Order To Prevent Excessive Power Consumption and Decrease the Life of the Motor and Battery.

This digital servo cannot be used with the following * AM * transmitters as the servo neutral signal is: 1310us). CONQUEST AM, FG Series (T4FG, T5FGK,T6FG, T6FGK, T7FGK), New Terratop, T3EGX, T3PGE, T2NL, T2LGX, T2FR, T2PK series.
For full performance use with FM, PCM and HR systems.

A note on Coreless motors. A conventional servo motor has a steel core armature wrapped with with wire that spins inside the magnets. In a Coreless design, the armature uses a thin wire mesh that forms a cup that spins around the outside of the magnet eliminating the heavy steel core. This design is much lighter resulting in smoother operation and faster response time.