Tariff amendment revises ad valorem customs duty rates on polysulphones and other plastics under Chapter 39. Amendment substitutes S. No. 11 in the Table to Notification No. 49/90-Customs (Chapter 39), replacing the entries for heading 39.11 to distinguish polysulphones from other goods and to assign separate ad valorem duty rates to each category, thereby creating a tiered ad valorem duty structure within that tariff heading.