This innovative pickup system is designed specifically to upgrade your Taylor guitar with a Taylor "Expression" system (2007 or later with 9V battery) to a battery-free Mi-Si system. It features a flexible circuit board preamp that retrofits in the side of the instrument. The preamp has active volume, bass and treble control knobs. Signal originates with a Baggs "element" under-saddle pickup and then routes to the preamp and out to the original Taylor endpin jack. And like all Mi-Si systems, the preamp is "charged" in 60 seconds with the included 1/4" jack-charger, which plugs into any 120/220 V AC-outlet (standard USA 2-prong plug). Professional installation highly recommened. Please note that these will NOT work in older Taylor 100 and 200 series guitars with ES-T or ES Blue systems.