The 70-450 Jar Store TM High Heat Button Lid is a continuous thread (CT) metal closure that offers excellent sealing properties of goods in your glass jars for extended shelf life. It is a Mason-style screw-on closure mechanism where the jar and lid are both threaded in one continuous bead around the entire circumference of the opening. The screw on canning lid is made of strong tinplate with a plastisol liner, a rubbery gasket that is attached to the canning jar lid. It is a common liner that is used for applications such as food canning and vacuum packing because it provides a tamper evident and hermetic seal (or airtight seal). The safety button on this regular mouth lid offers assurance of vacuum seal and tamper evidence.