The previous version of the iPhone introduced in September 2015. The 6s and 6s Plus are nearly identical in size to the iPhone 6/6 Plus but come with the faster, more battery-efficient A9 processor, an improved fingerprint scanner and camera (see Live Photos). Concurrent with the 6s/6s Plus is the debut of iOS 9, which has numerous new features (see iOS versions). The Force Touch feature, introduced on the Apple Watch, was renamed 3D Touch in the 6s/6s Plus, providing two levels of touch pressure to activate functions. New "peek" and "pop" gestures were added to access functions within an app. A Four-Inch 6s In March 2016, Apple introduced the iPhone SE; a similar high-performance phone but with a 4" screen (see iPhone SE). See iPhone 6, Force Touch and iPhone.