Customs duty exemption caps payable duty for high-purity copper sheets used to make solar selective coatings. Exemption from basic customs duty is provided for electroplating grade copper sheets of not less than 99.9% purity in continuous coils under heading 74.09 imported for manufacture of black continuously selective coatings used in solar thermal systems, limited to duty up to the amount calculated at the rate of 10 per cent ad valorem, and conditioned on production of a prescribed governmental certificate confirming the required end use.