Hobbywing SkyWalker UBEC 50A 2-4S Lipo Switch Mode 5V/ 5A Speed controller Brushless ESC for RC Drone Helicopter Aircraft 5V/ 5A Brushless ESC :Output Capability: Continuous Current 50A, Short-Time Current 65A (Less Than 10 Seconds) Power Input: 2-4S Lipo Pack Or 5-12 Nimh / Nicd Battery Pack BEC Output: 5V @ 5A (Built-In Switch Mode Regulator BEC) Maximum Speed: 210000 2-Pole Motor Rev / Min, 6 Pole Motors 70,000 Rev / Min, 12 Pole Motors 35000 Rev / Min Size: 68mm (Length) x 25mm (Width) x 12mm (Height)