calibre has a modular device driver design that makes adding support for different e-reader devices easy. At the moment, it has support for the SONY PRS 500/505/700, Cybook Gen 3, Amazon Kindle (1 and 2) and the iPhone (with the stanza reader software). Syncing supports updating metadata on the device from metadata in the library and the creation of collections on the device based on the tags defined in the library view. If an book has more than one format available, calibre automatically chooses the best format when uploading to the device.