PTFE fiberglass non-stick release liner made of selective fiberglass fabric, with nonstick coating ---PTFE on both sides, as the non-stick coating, cleaning it typically requires little work---you need only wipe or wash away any food or spills once the liner has cooled.
It is a tray or pad placed on a bakeware's bottom rack to catch food and liquid spills before the spills can collect and burn on the hard-to-clean cookware bottom.
Advantages: