The folks at Mercury Intermedia have released their iOS 9.3 UI kit in Adobe Illustrator vector format. It is the most complete and up to date iOS UI Kit released to date. Unlike many UI kits created in raster image format (typically PSDs), this one is so much more flexible because all the items are full vectors—making them perfect for mockups.
The iOS 9.3 UI kit is free to download, and weighs in at about 29MB in size. The file also comes in SKETCH format. If you have any reason to re-create iOS screen, this is a must-have!