Excise exemption for artificial staple fibres and tow limits duty to a fixed per kilogram rate under central rules. Artificial staple fibres and tow under sub heading 5502.00 are exempted from central excise duty insofar as the duty exceeds the amount calculated at a specified per kilogram rate, under sub rule (1) of rule 8 of the Central Excise Rules, 1944, with reference to the Schedule to the Central Excise Tariff Act, 1985.