PTFE envelope gaskets are available in slit, milled, formed shield, or double jacket styles. Slit envelope gaskets are essentially ring gaskets with 0.020″ thick leaves slit from the OD to approximately 3/64″ from the ID. These slit envelope gaskets are the most widely used gasket type in sizes for 1″ to 12″ OD. Milled envelope gaskets are made from PTFE cylinder stock, machined from their OD to within 3/64″ of the ID. These gaskets provide positive, trouble-free sealing in most applications ranging from mild to severely corrosive environments. Ideal applications for PTFE envelope gaskets include uses in equipment employing alloy, standard steel and glass-lined flanges; plastic, ceramic, and other types of flanges, and conical end glass pipe.