Free OS UI (User Interface) Kits PSDs
Below is a small collection of OS UI Kits PSDs are all fully-scalable psds and are free from freebiesbug.
iOS8 GUI – Free PSD
iOS8 UI kit for Sketch
“An extended and updated iOS8 UI kit for Sketch. It has been released by Rafael Conde on Github.”
Yosemite UI Kit for Sketch 3
Time Machine – Mobile calendar PSD
Music app UI