Listen to music inside or outside your home without running speaker wires or power outlets! Grace"s high-quality, weather-resistant speakers are perfect for wet or dry areas anywhere inside or outside your home. Powered by 900MHz 2-channel Phase Loop Lock circuitry they automatically lock in and keep the audio signal strong and clear within a range of up to 150 feet. The high powered wireless signal works through walls and other obstacles. The GDI-AQSHR21 are accessory add on speakers. Add this pair of speakers to any of the Grace Digital audio core wireless systems. These accessory add-on speakers will work with the following Grace Digital wireless speaker systems: GDI-AQBLT300, GDI-AQRCK400, and GDI-AQSHR200. The speakers are dual powered. They can play for hours of enjoyment on battery power or plug them into nearby AC power outlets. Enjoy your music without wires - with Grace.