This is the Futaba S9002 Mini Coreless Servo.

FEATURES: Ideal for electric and mini cars, small electric airplanes and
small electric helicopters
Compatible with the Futaba GY401 Gyro (FUTM0807)
Dual ball bearings insure smooth operation


INCLUDES: Futaba S9002 Mini Coreless Servo with 0.79" (20mm) diameter round
horn, 1.4" (35mm) diameter round horn, 1.2" (32mm) diameter 6
point horn, 1.5" (38.5mm) diameter 4 point horn and mounting
hardware


REQUIRES: Installing in model, connecting linkage and connecting to receiver


SPECS: Torque: 34oz-in (2.5kg/cm) @ 4.8V
43oz-in (3.1kg/cm) @ 6V
Speed: 0.18 sec/60° @ 4.8V
0.14 sec/60° @ 6V
Size: 1.2 x 0.6 x 1.2" (1-1/4 x 5/8 x 1-1/4") (31 x 16 x 31mm)
Weight 1.1oz (1-1/8oz) (31g)


COMMENTS: A note on Coreless motors: Conventional servo motors have a steel
core armature wrapped 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 results in smoother operation and
faster response time.