( 1 ) BY the present writ petition, petitioners seek to, interalia, challenge the Directive No. 15/16/63-CXI of the Central Board of Excise and Customs, respondent no. 2 herein, whereby it has been clarified that, where an exemption of set off is given under the notification, the special duty of excise is to be calculated first, without applying the exemption notification, which is to be applied thereafter.

( 2 ) TO appreciate the respective contentions of learned counsel for parties, it will be useful, to refer to, in briefs, the facts of the case.

( 3 ) PETITIONER No. 1 manufactures tyres, tubes, flaps and rubber products, which are classifiable under Tariff Items 16, 16a and 68 of the 1st Schedule to the Central Excise and Salt, 1944, hereinafter referred to as the Act. In the manufacture of finished products, petitioner Company uses certain raw materials, which are classified and, on which duty is paid under Tariff Item 68 of the 1st Schedule to the Act. Petitioner, also uses synthetic rubber, carbon black and rubber processing chemicals, in the manufacture of rubber products. These products, are, hereinafter, referred to as the inputs.

( 4 ) ON June 4, 1979 the