ZTW is one of the two largest ESC manufacturers in China, and one of the largest OEM ESC suppliers to many RC model manufacturers and dealers worldwide.
TW Spider Series ESCs are high quality speed controllers designed specifically for multi-rotor aircraft. Flashed with popular SimonK firmware for multi-rotor. Spider Series ESCs feature up to 600Hz refresh rates for an incredibly smooth yet crisp flight controller response. These ESCs also feature excellent throttle linearity without sacrificing a rapid, crisp response to throttle input. As usual. Spider Series ESCs come standard with the ZTW quality, performance, and reliability you have come to trust.

Flashed with SimonK firmware (v11.9.2013)
Extremely low internal resistance
Super smooth and accurate throttle linearity
Safety thermal over-load protection
Auto throttle shut down in signal lose situation
Supports high RPM motors
Power arming protection (prevents the motor from accidentally running when switched ON)
Use new generation of the MOSFETs to make sure the ESC with low heating and more reliability

Specifications
SimonK version: 11.9.2013 
Output: 30A continuous, 40A burst
Max power: 500W
Input Voltage: 2-6s lipo
BEC Output: OPTO (NO BEC)
Dimensions: 43 x 25 x 10 mm
Weight: 26g