Our plastic autoclavable regular mouth mason jar lids are built to be functional and affordable. Designed specifically for liquid culture cultivation, they feature a hydrophobic PTFE filter which can be held upside down and not leak. Our lids feature super heavy duty medical grade self-healing injection ports, and we seal each hole with high temperature silicon. Each lid comes with a reusable silicon gasket ring for an airtight seal. This type of lid must be left a 1/4 turn open when pressure cooking, and fully tightened when cooled. 1/2" heavy duty self-healing injection port regular mouth polypropylene plastic autoclavable lid sealed using high temp red RTV gasket silicon .45um PTFE air-exchange filter silicon gasket ring for airtight seal