This is the Hitec HSC-5998TGS Ultra Hi-Torque, Hi-Speed Digital Servo.
Designed to be used with cars, primarily for steering.
Universal connector for use with Airtronics Z, HiTec & JR.

FEATURES: Digital Technology
Coreless motor, a conventional servo motor has a steel core armature
wrapped with with wire that spins inside 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 is much lighter resulting in smoother operation
and faster response time.
Dual ball bearings
Titanium-Alloy gear set

INCLUDES: One HSC-5998TGS Ultra Hi-Torque, Hi-Speed Digital Servo
One servo horn
Four rubber grommets
Four mounting screws
Four brass eyelets
One small decal sheet
One instruction sheet

REQUIRES: Mounting to model

SPECS:    Torque:  @ 4.8volts - 200 oz  (14 kg)
@ 6.0volts - 250 oz_ (18 kg)
Speed:   @ 4.8volts - 0.23SEC
@ 6.0volts - 0.19SEC
Size:    1.6"x0.8"x1.4"  (40x20x37mm)
Weight:  2.18 oz.  (62 g)

COMMENTS: Gear Set: 55310
Case Set: 55414 (HRCM5414)
Horn Set: 55714