Pewter 70G450 Canning Lid Unlined has a continuous thread, meaning that 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. This makes it easy to open while still being very secure. The screw on canning lid is made of strong tinplate. Pewter has a vintage antique look in a fashionable way, which makes this canning lid perfect for birthday parties, bridal showers, and wedding receptions.