State-of-the-Art Wireless 900Mhz RF Speaker Bundle with 2 Add-On Speakers and Accessory Power Card Reader and Screen Protector - Superb Sound Thru 4 of the Highest-Quality Wireless Hybrid Speakers Around Powerful bass and crisp, clean treble through a wireless speaker system that gives you 150 feet of mobility Durable, weather-proof speakers have individual volume controls so you can adjust levels depending on speaker placement Intuitive 900 Mhz Digital RF transmitter equipped with a 3.5mm audio jack for iPhone / iPod / MP3 Player / TV / CD / DVD / Blu-Ray compatibility Phase Loop Lock (PLL) circuitry automatically locks in and keeps audio signal clear and strong Accessory Power SD Card Reader and Screen Protector make this bundle a great deal! Speaker set is manufactured by Cables Unlimited and the Card Reader and Screen Protector's are manufactured by Accessory Power