Section 07 Plastics and articles thereof; rubber and articles thereof 40 Rubber and articles thereof 40 02 Synthetic rubber derived from oils, in primary forms or in plates, etc 40 02 31 Isobutene-isoprene (butyl) rubber 40 02 31 00 Isobutene-isoprene (butyl) rubber Commodity Code Description 40 02 31 00 00 Isobutene-isoprene (butyl) rubber
