Icons that included in the sets are very common ones that any UI design can require (Communication, Media, Signs & Symbols, Developers icon, Tools, Settings & Display, files & Foldes, Office & Finance, Graph, Shopping Cart and Icons which are very useful to creating such interfaces).
Every designer who has spent many hours mocking up web pages, mobile apps or app icons will tell you how important it is to have a reliable set of re-usable, editable and uniform GUI elements that they can rely upon for the initial rapid prototyping stage of any project.
So what are you waiting go ahead and download the lovely free outline icons for next web or design project.
NOTE: Free icon sets you can download and use both for commercial and non-commercial aims.
Odincons 100% Shape Outline (100 Icons)
3px Outline Icons Set
Free PSD Outline Icons (220 Icons)