Description:
This hardware, with the SimonK firmware, gives you the perfect solution for multirotor use:
Highest efficiency 100% N-FET design.
Highest accuracy with Crystal Oscillator (Temperature won't affect the PWM operating range like other cheap ESC's).
No low voltage cutoff, because any cutoff in a multirotor = crash.
No over temp cutoff, because any cutoff in a multirotor = crash.
Super high refresh rate, no buffering of the input signal, resulting in more than 490Hz response rate.
16KHz motor frequency, giving fastest response of the motor, and quietest operation as well (no 8KHz squeal).
Super simple, foolproof operation! Nothing to program other than the throttle range.

ESC Specifications:
Max cont. current: 40A
Peak current: 50A (10s)
Voltage: 2-4S lixx, 
BEC: 5V/3A
Size: 55x24x11mm
Weight: ~28g

Packing content:
4pcs 2-4S 40AMP 40A SimonK firmware Brushless ESC