This device plugs inbetween the Rx and the speed controller. It allows the user to program the BESC according to a series of LED indicators. it has buttons at the bottom so you can navigate through the menu and select the feature you want, then change it. Its very simple and is much easier than listening to jingles or a series of beeps. This item is an excellent addition to your flight kit, and lets you quickly change the BESCs settings in the field in a much shorter time and with greater assurance that what you have changed is correct and saved into the BESC.