TCO 0505865 makes a specific industrial chemical mixture—barium sulphate, calcium chloride and crystalline silica (HS 3824.90.90)—eligible for item 50 in Part III of Schedule 4 to the Customs Tariff Act 1995 from 16 May 2005 until revoked. Mechanically it changes the tariff treatment applied to those imported goods. The order was made by a delegate under s.269P of the Customs Act 1901 and may be revoked under ss.269SC/269SD. Importers who show imports match the listed description may pay lower duties; customs determines eligibility.