Compatible with iPod with dock connector (10GB, 15GB, 20GB) 3rd generation. Dock adaptors enable any iPod model to connect to the iPod universal dock and other products that use the universal dock system. Simply insert the dock adaptor that fits your particular iPod model into the dock, then plug in your iPod. When you want to connect a different-size iPod, simply pop out the dock adaptor and insert a new one.