These dampeners are designed to be printed with TPU to have a softer surface than the original mount. Instead of these parts you can also use some rubber or felt you may have lying around.
Simply print the parts with TPU. They will be softer if you reduce the amount of infill or walls. If you want to add them to every holder part, simply print them in the specified amount.
For installation, it's best to use some double-sided tape to hold them into place while installing the holder and PC.
The author remixed this model.
Dampener for the original PC holder parts.