This is the BK Servos DS-3001HV High Voltage Metal Gear Digital Micro Cyclic Servo. BK micro servos feature a mini size servo motor shoehorned into a micro size servo case, this allows for blazing speeds combined with good centering and plenty of torque. This servo features a micro-size upper case, making it suitable for any helicopter that uses a micro size servo.
- Operation Voltage: 5V – 7.4V
- Weight: 20g (.71 Oz)
- @ 5V: 3.68 kg/cm (51.1 oz/in)
- @ 6V: 4.7 kg/cm (65.3 oz/in)
- @ 7.4V: 5.8 kg/cm (80.4 oz/in)
- @ 5V: 0.09 sec/60
- @ 6V: 0.07 sec/60
- @ 7.4V: 0.06 sec/60
- Dimensions: 12x23x27mm
- Frequency: 1520us/333 hz
- Gear Type: Metal
- Motor Type: Coreless
But if you can afford it, go for XPERT CI-2401-HV brushless micro servos.
Those are the best on the market.
And use KST 215MG gears if you want better rigidity.