Features: Safety Arming Feature: Regardless the throttle stick position， the motor will not spin after battery connected.Throttle Calibration: Throttle range can be configured to provide best throttle linearity， fully compatible with all market available transmitters.Selectable program settingFull Protection Features: Low voltage cutoff protection / Over-heat protection / Throttle signal lost protection.Description:Item Name: Hobbywing SkyWalker 40A UBECConstant Current: 40ABEC Mode: Linear modeBEC Output: 5V at 3AInput Voltage: 2-3S Lipo， 5-9 cells NiMH.Dimension: 68 x 25 x 12 mmWeight: 43gMaximum speed: 210000 RPM (2 poles motor)， 70000 RPM (6 poles motor)， 35000 RPM (12 poles motor).Usage: Apply for 400/450 helicopter 3D， and 32 level fixed wing sportsPackage size:?? 10 * 10 * 2 cm / 4 * 4 * 0.8 inPackage weight: 48 g / 1.7 ozPackage list:1 * Original Hobbywing SkyWalker 40A Brushless ESC