This knob has embedded JavaScript that lets you turn the knob and change its value. This could perhaps be used instead of a slider in certain applications. Here is an example of how it might be used.
The brushed metal look is various lines created at random in JavaScript, so the lines change each time you reload the page.
It might be possible to generate the look just one time and save the values as static SVG elements, but this increases the file size from about 7,000 bytes to about 12,000 bytes, an increase of 70%. We ought to test whether the overhead of transmitting the extra bytes offsets the the time it takes for the browser to render the texture in a JavaScript loop.