Hobbywing 20A Skywalker Quattro 20Ax4 UBEC 4 in 1 20A Brushless ESCs 190882741464 4 speed controllers in 1 board, only 1 pair of battery wire is required. Powerful switch model built - in BEC (the BEC voltage outputs from the S3 connector) Multiple protection features: Low voltage cut-off protection/ over-head protection/ throttle signal loss protection. The throttle range of each ESC can be calibrated to be suitable for different multi-rotor flying control systems/transmitters.