S8955SS 2K with big block top case and larger gears.
Reinforced and redesigned top case and gears make the servo more than durable than ever.  New design helps prevent wiggling pins inside the top case which could create gear gap during flight and could be a cause of damage to the gears.
 
Stall torque:   34.2 (6.6V) / 38.3 (7.4V) / 43.5 (8.4V) kg · cm
                          474.7 (6.6V) / 532.2 (7.4V) / 604.1 (8.4V) oz
Speed : 0.06 (6.6V) /0.06 (7.4V) /0.05 (8.4V) Sec / 60 °
Weight: 85.5 g / 3.02 ozLead length : 300mm
Operating voltage: 4.5V – 8.5V
Operating angle: 120 ° / 150° / 180 °
Programmable
Recommended for giant scale ailerons .Jet- Good response on jets.
 
Important Notes on Using Our Servos
Our servos are programmed to operate with high precision and sensitivity.
Because of this, if there are any obstructions within the servo’s range of motion and it is unable to move as commanded by the transmitter, the servo may experience excessive load. This can result in damage to the internal circuit board due to overheating.
When installing the servo for throttle, aileron, or other control surfaces, please make sure to leave a small amount of free play between the servo travel range and the mechanical movement range. This helps prevent any binding or overloading of the servo.
 
The firmware in a 2k servo verifies the position of the servo arm two thousand times each second, 
while the firmware found in previous servos verify the arm's position one thousand times per second.
This greater number of verifications makes for a very precise servo, and gives it a more "solid" feel.
It is recommended to use a booster cable with 2k servos to ensure steady voltage at all times.