BLS173SVi High Voltage Metal Gear Mini Servo from Futaba - FUTM0184
The Futaba BLS173SVi is a programmable S.BUS2 high voltage metal gear mini-sized servo that excels in 600 size helicopters but can also be used in larger aircraft up to 2000mm wingspans. Uses a brushless motor.
Features:

Designed for airplane, glider and EP helicopter applications
High voltage and high torque
Programmable S.BUS2 platform
Brushless motor
Metal gear train eliminates backlash and slop
One year warranty

Includes:

1x BLS173SVi high voltage metal gear mini servo
1x 0.81" (20.5mm) round horn
1x 1.5" (39mm) 4-point horn
1x 1.2" (32mm) 6-point horn
4x each grommets, eyelets, and screws