Hobbywing FlyFun ESC series- The deluxe ESC by Hobbywing, built for advanced users
For Multi-Rotors, you'll need a reliable speed controller, and this is exactly the one you need. Price is good, the quality is good, we put this on our 7kg drone to do aerial filming, powered with 6S 22.2V 16000mah battery, flew for 15 minutes, when it land this ESC is around 40 degrees C (it's warm, not very hot), that means energy has converted into motor rotation efficiently.

OPTO means this ESC lacks of the BEC Circuit, BEC circuit is to convert the battery's input voltage to 5V for powering the Receiver. Most of the expensive Flight Controllers (e.g. DJI NAZA) has a BEC unit included, so many players will use OPTO ESC to save money and less work load on the ESC. However, if your Flight Controller has NO BEC included, you will need to purchase an UBEC module (5V) to power up the RC Receiver.

Features :
- Safety arming feature: Regardless the throttle stick position, the motor will not spin after battery connected.
- Throttle calibration funtion: Throttle range can be calibrated to be compatible with different transmitters.
- User programmable. 
- Multiple program methods supported: transmitter stick, LED Program Card. Very easy to program the ESC at home or at the flying field.
- Compatible with Lipo battery and NiCd/NiMH battery.
- Internal timing can be changed to be suitable for different brushless motors.
- Full protection: Low voltage cutoff protection / Over-heat protection / Throttle signal loss protection.
- Extreme low resistance PCB is used at the power output section, the whole ESC has super current endurance capability.
- Microprocessor uses separate voltage regulator IC, with good anti-jamming capability.

Specification :
- Output: Continuous 40A, Burst 55A up to 10 seconds.
- Input Voltage: 2-6 cells lithium battery or 5-18 cells NiCd/NiMh battery.
- BEC: NO BEC
- Refresh rate of the throttle signal: 50Hz to 432Hz.
- Max Speed: 210000rpm for 2 Poles BLM, 70000rpm for 6 poles BLM, 35000rpm for 12 poles BLM. (BLM = BrushLess Motor)
- Size: 60mm x 28mm x 12mm..
- Weight: 35.2g

Includes:
- 1 X Hobbywing FlyFun 40A OPTO ESC
- 1 X English Manual.

* You will need 3.5mm banana plugson the brushless motor side.