Numix-Circle Linux Desktop Icon Theme is licensed under GPL, The GNU General Public License, which means you can download and use it freely. If the above sample wasn’t enough to get you warmed up towards the circlet-ish icon theme, then perhaps the following examples will:
Download icon set
So now that you see the whole picture (pun intended), you’re probably interested in downloading and start using it right away, if you are an Ubuntu or one of its derivatives user then you can simply:
sudo apt-get update
sudo apt-get install numix-icon-theme-circle
via Terminal. Other distros may Download it from GitHub, extract the ZIP file and copy paste the folders into your /usr/share/icons folder.