The Castle Creations B Link Bluetooth Adapter gives you access to powerful Castle Link ESC tuning features right from your smartphone! Castle Link is an essential component of customization for all Castle ESCs. While the controllers are plug and play, the benefits of fine tuning your Castle ESC through the Castle Link Programming Suite have only reinforced the sophistication and value of the Castle product line. Not only do you get the ability to adjust many variables to enhance your experience, you have the assurance that firmware updates for future features and improvements for your controller are provided at no cost to you.