Ceramic Coated Headers With A Thermal Barrier. Designed for: 66-74 B-body and 70-74 E-body With Stage 5 Heads. Primary tube size: 2-1/4″ O.D.Collector Size:4″ 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.