Polished Ceramic Coated With A Thermal Barrier 2-1/8″ B1/B1BS Step Headers. Designed for:62-74 B-body and 70-74 E-body With Big Block.Primary tube size: 2″ O.D. Secondary tube size: 2-1/8″ O.D.Collector Size: 3.5″ With 3-bolt flange. Flanges: 3/8″ thick, laser-cut, contoured for a leak free fit. For more details visit the TTI Website.Price does not include shipping. FOB from Corona, CA 92880-1726 . Shipping can be very expensive depending on your location. For an accurate shipping rate please call us.