Note:There are 4 options for your choice, please according to the pictures choose the one you need. Specification: Weight: 25g Dimensions: 45 x 24 x 11mm Power input: 5.6V - 16.8V (2-3 cells Li-Poly, OR 5-12 cells Ni-MH Ni-MH / Ni-Cd battery) BEC: 2A Constant current: 30A (Max 40A less than 10 seconds) Features: - Safe power function:regardless of the throttle stick in any position the motor will not start immediately - Throttle Calibration function:Adapt to different remote throttle travel difference, improve throttle response linearity, with a smooth, delicate feel and excellent speed linear speed - Low Voltage Protection Mode ,Low-voltage protection threshold Pakacge Included: 1/4 x 30A Brushless ESC(optional)