Grace Digital GDI-AQSHR21 Indoor/Outdoor Water Resistant Add-On Accessory Wireless Speakers (Discontinued by Manufacturer) 900 MHz wireless technology for up to 150' foot range to listen to your stereo, iPod, or TV outside on your yard or patio These are ACCESSORY wireless speakers. You must have a Grace wireless transmitter to play these accessory speakers Control the volume via your audio source or directly on each speaker Full range, high powered downward facing speaker for full 3-D audio sound in your room or outside patio Connect the GDI-AQSHR21's to any of the Grace transmitters