This is the Futaba S3156 Micro Digital Metal Gear Servo.

FEATURES:
For small electric powered aircraft models


INCLUDES:
Futaba S3156 servo, 0.79" (20mm) long 4-point horn, 1.6" (40mm) long
4-point horn, 0.79" (20mm) diameter round horn, four 2x11mm
mounting sccrews
One year limited warranty


REQUIRES:
Installing in model, connecting linkage and connecting to receiver
Order DUBM6924 if mounting hardware is needed


SPECS:
Torque: 28 oz-in (2.0 kg-cm) @ 4.8V
33 oz-in (2.4 kg-cm) @ 6V
Speed: .13 @ 4.8V
.11 @ 6V
Size: 0.9 x 0.4 x 0.9" (22 x 11 x 22mm)
Weight: .32 oz (9.3g)


COMMENTS:
Do not use this servo with gas powered models or models requiring
high torque.
Do not exceed 6V supply voltage or apply high load to servo.
Do not use standard size servo horns. Use horns designed only for
micro servos.
For replacement horns use part numbers FUTM2005 or FUTM2038, they
fit very tight but they will work.