This four pack of 35 amp multi-rotor ESCs features three ESCs without a BEC and one with a BEC. Each ESC has optimized firmware specifically designed for quadcopter and other multi-rotor platforms. Refresh rates of up to 490 Hz give your platform optimum stability and maneuverability without missing a beat. QuadPack 35 comes preprogrammed for Multi-Rotor platforms and is recommended for platforms ranging from 450 to 650 sizes, pulling up to 35 amps, and running up to a six cell LiPo. Easily programmable using the Castle Link USB adapter (sold separately).