Download all Firefox OS UI components in one single file and create quick mockups of your applications by just making drag and drop. The layered PSD (Photoshop) contains editable effects, fonts and shapes so you can easily customize your app.
You’ll find different icon sets, from primary action icons to communications, settings and media icons. They’re available as layered PSD files in vector format, so they’re ideal to be used in different devices no matter the screen size without loosing quality.
The default font used in Firefox OS is "Fira Sans". You will find it in four different weights: Light, Regular, Medium and Bold. Please, refer to the license file to check font's usage permissions.