This is the Futaba S9254 Digital Coreless High Torque,High Speed Helicopter Gyro Servo with J Connector.

This servo can produce high-current draw from your batteries.If using NiMH or LiPo batteries, make sure they are capable
of delivering sufficient amps.
FEATURES: Coreless motor for reduced weight and high-speed response
Digitally enhanced microprocessors cut the response time in half
from transmitter input to servo reaction
Dual ball bearing gear train
Dust and water resistant-not water proof
Nylon gears
Black plastic case
INCLUDES: One S9254 Digital Coreless High Torque High Speed Helicopter Servo
One round servo wheel, one six arm servo horn, one four arm servo
horn, four grommets, four mounting screws and four rubber mounts.
SPECS:    Speed:        0.06 sec/60° @ 4.8V
Torque:       47 oz-in @ 4.8V
Dimensions: 1.6  x 0.8 x 1.4" (40 x 20 x 37mm)
Weight:       1.7oz (49g)
Power Supply: 4.8V (Futaba does NOT recommend using 6V)