Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Radioactive GUI for NGUI Free.
Radioactive GUI v1.0
** Requires NGUI v3.4.9 or later to work **
Radioactive GUI for NGUI – contains a test scene where you can see all the components in action. Fonts and textures are in one atlas. Source .psd files provided for all components.
Check it out in WebPlayer!
If you’re looking for a standard Unity guiskin version – it’s available on the Asset Store here.