The BLS-43a is hands down the best servo under 100 bucks! It is packed with features that only the highest end servos have. An all metal cnc machined construction, loads of speed and as much torque as you could want in this class of servo.
 
Soft Start Protection
Over Voltage Protection
Low Voltage Protection
Locked Rotor Protection 
Temperature Protection
Includes Aluminum Servo Arm
 
Applications
Excellent for 3D Airplane, Large Jet & 1/5、1/8th Buggy, Truggy, Crawler,   
Monster & Helicopter.  (EP / Gas / Nitro)
 
Specifications
Torque At 6.0V
     35.5 kg-cm / 493.1 oz-in
Torque At 7.4V
     43.8 kg-cm / 608.4 oz-in
Torque At 8.4V
     49.7 kg-cm / 690.3 oz-in
Speed At 6.0V
     0.13 sec / 60°
Speed At 7.4V
     0.11 sec / 60°
Speed At 8.4V
     0.10 sec / 60°
 
Power Supply
Operating Voltage
Range
 4.5V ~ 8.5V ( 4 ~ 6 Cell Ni-MH or 2S Li-Poly / 2S Li-Fe)
 
Standard Full Aluminum Servo
Control System
   Digital Controller / AD 12-Bits Resolution ( 4096 Steps )
   Frequency：333Hz / Neutral：1520us
Dead Band Width
   0.001ms ( Default：1us)
 
Mechanical Specifications
Ball Bearing
   Dual
Gear
   Titanium Alloy Gears
Motor
   High Premium Brushless Motor
Horn / Gear Spline
   25 Teeth ( Same as F-Type )
 
Physical Specifications
Dimension (mm)
    40.5 x 20 x 39 mm / 1.59 x 0.79 x 1.54 in
Weight (gram)
    78.5 ± 1 grams / 2.77 oz