There have been four versions of the iPad Mini, all of which have a screen size of 7.9 inches (20 cm). The first generation has similar internal specifications to the iPad 2 but uses the Lightning connector instead. The iPad Mini 2 added the Retina Display, the Apple A7 processor, and the Apple M7 motion coprocessor, closely matching the internal specifications of the iPad Air. The iPad Mini 3 added the Touch ID fingerprint sensor. The iPad Mini 4 features the Apple A8 and the Apple M8 motion coprocessor.