The shape of a gear, which can be used on an options/settings button. This is the same shape as the clipart submitted by FrancescoPallucchini, but the SVG markup has been greatly simplified, making it easier to include inline in HTML or other projects, and also easy to change the color using CSS.
Option button symbol (minimal SVG markup) free icon was designed by CrazyTerabyte for icons Png and presented to its users.
CrazyTerabyte
1/1/2018