Flat UI Kit
PNG source file, for Adobe Firewords.
Flat UI Kit is a free design resource made by Dribbble user Corey Haggard. As far as I can tell, its license is .
Helpful hint: Dribbble users are nice. If the license is unknown, it is usually because they forgot to mention it explicitly; not because they were being stingy. Ask nicely and they will probably allow you to use it.