Customs duty cap on specified bulk drugs limits liability to a fixed ad valorem rate, exempting excess duty. The Central Government, invoking its statutory power and public interest, exempts specified bulk drugs (including salts and esters) from customs duty to the extent that such duty exceeds a stated ad valorem rate; the notification lists Pilocarpine, Sulfadoxin, Sulphamethoxypyrazine and Salazosulphapyridine as the eligible imported goods.