Energy saver circuitSupplied with built in 2 magnet rollerTotally sealed and waterproofUltra-bright white LEDInterchangeable rollerSilent mode5 tone and volume levelOversized and powerful speakerInterchangeable roller4 roller each color with one magnet4 roller each color with four magnet150m wireless rangeDifferent illumination on receiver for run or drop back indicationMemory function on receiverSilent mode and vibrationSupplied with Neoprene ultra soft coverUses one piece of 4A76 6V battery