These knobs are highly detailed, heavy and smooth. To keep the price down, the knobs are unfinished. They have been printed from white ABS resin, Washed and cured. 
 
They require gentle sanding with 600 Grit sandpaper, and paint should be applied once cleaned. I highly recommend using a primer first. Once dry, black wax can be added to the knobs for text.
 
There is a video of how to finish these knobs on: Youtube.
Skip to time 11:50 for the start of the knob section.
 
I have tried to include as many photos of the parts to show the details close up and the parts that will require sanding due to support removal.