This is the Futaba S3151 Digital Servo.
Great for a wide variety of R/C models.

FEATURES: Digital technology gives performance advantage
One Ball Bearing and one Metal Bushing
Nylon gears
One year warranty

INCLUDES: One S3151 Digital servo with preinstalled servo horn
Four Rectangular Grommets
Four Mounting Screws
One Large Round Horn
One Six Arm Horn
One Four Arm Horn

SPECS:    Speed:  0.21 sec/60° @ 4.8V

Torque:   43 oz-in  @ 4.8V
Dimensions:  1.6 x 0.8 x 1.4 in (41 x 20 x 36mm)
Weight: 1.5oz (42g)