This is the HS-7954SH High-Voltage Ultra Torque Digital Servo from Hitec.

FEATURES: Ideal for giant scale planes, large helicopters, rock crawlers,
monster trucks, 1/8 scale trucks and buggies and anywhere a high
performance, high torque servo is needed
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
Steel gears for much longer life than conventional metal gears
Nine O-rings for extra resistance to moisture and dust
Capable of operating on two cell LiPo packs

INCLUDES: HS-7954SH High-Voltage Ultra Torque Servo, 1.8" (45mm) diameter round
horn, 2.3" (59mm) long double sided horn, 2.8" (72mm) long double
sided horn, 1.3" (34mm) single sided horn, 0.83" (21mm) single
sided aluminum horn, 0.98" (25mm) single sided horn, four each
grommets, eyelets and mounting screws, instruction sheet

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

SPECS: Size: 1.57 x 0.78 x 1.45" (40 x 20 x 37mm)
Weight: 2.30oz (65.2g)
6.0V 7.4V
Speed: 0.15 sec 0.12 sec
Torque: 333 oz/in 403 oz/in
Wire Size: 22 gauge twisted wire with gold plated connectors
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.