Emaxs BLHeli Series 20A ESC with Oneshot is designed specifically for FPV racing. The Emax series is a line of high-performance and low-cost ESCs for drone motors. Emaxs ESCS are 100% guaranteed original and genuine products for the beginner who wants to learn how to build a drone. EMAX BLheli series 20AESC is a brushless dc motor speed controller. The low output resistance greatly enhances power stability because The ESC is adapting a2-4S Lipo battery which improves good battery life.Rotation direction of the motor is programmable: normal, reverse or bidirectional .All parameters can be programmed via using a program card or a transmitter, including default settings .Multiple protection features including low voltage cut-off protection/over-heat protection/throttle signal loss protection .Alarm to help you find the devices: keep the throttle on FULL ON position for a while, the ESC will help Throttle range can be configured and is fully compatible with all receivers, providing smooth, linear and precise throttle response