Excise tariff amendment replaces table entry for polystyrene copolymers, changing the specified ad valorem duty under notification. The Central Government amends the table to Notification No.133/86-Central Excises by substituting, against the relevant serial entry for polystyrene and certain copolymers of styrene, the entry in column (4) with Forty per cent ad valorem, thereby changing the ad valorem duty specification for the item listed under Chapter 39.