Excise exemption for magnetic tapes limits duty to a specified per area rate, capping excess liability under rule 8. Exemption limits excise duty on magnetic tapes for sound recording under Chapter 85 by capping liability to the amount computed at a specified per square metre rate, with the Central Government acting under sub rule (1) of rule 8 of the Central Excise Rules, 1944 to exempt duty in excess of that prescribed per area amount.