Customs classification: specified goods under medical and optical headings attract a reduced duty rate under the Fourth Schedule. The Fourth Schedule applies the interpretative rules of the First Schedule to the Customs Tariff Act, 1975 - including Section Notes, Chapter Notes and General Explanatory Notes - and prescribes that all goods falling under headings 9018, 9019, 9020, 9021 and 9022 of the First Schedule are subject to the rate of duty specified in this Schedule.