This is a Hitec HS-81S Micro Servo.  These are great for small electric planes, helis, and small cars.  This has the universal connector that works with JR, Hitec, Futaba, and Airtronics, and also works with some micro RTR vehicles (check with manufacturer of micro car for compatibility).

FEATURES:
Compact, Lightweight Design-Ideal for Electric cars, airplanes, and sailplanes
Strong, Dependable Gear Train
High Torque and High Speed
Mounts with Two Screws

INCLUDES:
One HS-81S Micro Servo with 6-3/4" connector wire.
One 7/8"x7/8" X-shaped servo horn
One 1-1/8" long straight servo horn
Two brass eyelets
Two mounting screws
Two servo grommets
One servo horn screw

SPECS:
Transit Speed: 0.11 sec/60deg at 4.8V
                          0.09 sec/60 deg at 6.0V
Output Torque: 36.10 oz/in at 4.8V (2.6kg/cm)
                          41.66 oz/in at 6.0V (3kg/cm)
Length: 1.17" (29.8mm)
Width:  0.47" (12mm)
Height: 1.16" (29.6mm)
Weight: 16.6g (0.58oz)
Mounting holes on-center: 1.31"(33.27mm)