Knots 2U only provides FAA-PMA approved aviation spark plug gaskets, not cheap imitations. These are manufactured to precise dimensions and material standards, based on the effective reach of a spark plug as determined by its installed thickness. An inferior gasket can result in exposed threads which will cause hot spots, initiate pre-ignition and potentially cause early plug failure.
Using new gaskets ensures a tight, gas-sealed spark plug. These all copper 18MM spark plug gaskets are FAA-PMA approved as a direct replacement for the gasket called out by the OEM, not a simple AN replacement that can vary in diameter and thickness.