Exemption for parts used in tractor manufacture extends to components classified outside Chapter 87 when used within the factory. The circular clarifies that goods excluded by Note 2(e) of Section XVII retain their original chapter classification (for example, internal combustion engines in Chapter 84) and are not reclassified under Chapter 87; however, notifications exempt 'parts, falling under any chapter,' used within the factory of production for manufacture of tractors under the tractor heading, so such components remain eligible for the exemption subject to the other conditions of those notifications.