Tethr brings to you the most beautiful iOS design Kit – ABSOLUTELY FREE of cost. It provides both Photoshop & Sketch templates, which the makers claim to be of worth $80. With this awesome free UI iOS UI Kit you get 8 source files, 138 templates and 250+ UI elements. Every nitty-gritty of the templates are taken care along with making it minimal and retina ready. You can mix and match the UI to create multiple types of app designs.
This is going to be great resource for designers and developers who want to quickly prototype their app.