SIRIUS Stiletto SL100 Portable Satellite Radio Receiver Portable receiver with a built-in antenna allows reception of Sirius signal Eliminates the need for an external car or home docking station Offers up to 100 hours of storage capacity and can handle MP3 and WMA files, enabling you to mix Sirius content with your own personal music collection Headphones come with two batteries, (one small and sleek; the other with extended life) and an indoor A/C adapter for charging the batteries Dimensions: 2.0 x 4.5 x 11/16 inches (WxHxD) with slim battery; 2.0 x 4.5 x 1.0 inches (WxHxD) with standard battery; weighs 4.3 pounds