The Spektrum™ 4000mAh 11.1V LiPo 30C Smart LiPo Battery is designed to be in the same size as a standard 2S pack. It allows drivers with 2S battery size limitations a great option for 3S power. Its unique size, shape, and 30C rating are custom-tailored for these vehicles. With Spektrum Smart LiPo batteries, charging parameters and performance data are stored and uploaded automatically to Smart chargers with a single IC5® connection!