This is the HS-7940TH High Speed, High Torque Digital Servo from Hitec.

FEATURES: Ideal for larger helicopters and cars needing high speed and plenty of torque Coreless motor for precise centering and accuracy
G2 programmable digital circuit, programmable features include; Dead Band Width Speed (reduction)
Fail Safe Position Direction (CW/CCW)
Fail Safe On/Off End Points
Overload Protection Resolution High/Low
Titanium gears don't break or develop slop like conventional metal
gears Capable of operating on two LiPo packs

INCLUDES: HS-7940TH High Speed, High Torque Digital Servo

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

SPECS: Size: 1.57 x 0.79 x 1.50" (40 x 20 x 38mm)
Weight: 2.40oz (68g)
6.0V 7.4V
Speed: 0.07 sec 0.06 sec
Torque: 181 oz/in (13.0kg/cm) 222 oz/in (16.0kg/cm)
Drivetrain Type: Dual ball bearing

COMMENTS: This servo can be programmed with any Hitec digital servo
programmer. However, the Overload Protection and Resolution High/
Low can only be programmed with the HFP-20, HPP-21
(HRCM4420) or the HPP-21+ (HRCM4421)

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