Freebbble!

There are a lot, and I mean a lot, of .sketch freebies lately. This is one of them.

Reamill OS X [.sketch] is a free Mockup design resource made by Dribbble user Fabio Basile. As far as I can tell, its license is Unknown.

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.