rubbish. learn nothing.
Take a look at a pack of 121 high-quality materials for Unity projects. These are said to be extremely lightweight with no quality loss. The materials are presented in Substance format (compatible with all Unity versions).
The pack allows you to set the resolution of your choice. The ‘Ultimate Material’ set also features special materials with customizable parameters.
What is more, the author is working on the future updates with new materials. And yes, you can request a material.