Ceramic Coated Headers With A Thermal Barrier. 1-5/8″ X 1-3/4″ Small Block Step Headers. Designed for: 63-66 A-body. Primary tube size: 1-5/8″ O.D. Secondary tube size: 1-3/4″. Collector Size: 3″ 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.